Automatic rearview mirror, vehicle lighting control and vehicle interior monitoring system using a photosensor array

ABSTRACT

A system apparatus, and method for controlling a plurality of variable reflectance mirrors (or mirror segments), including a rearview mirror and side view mirrors, which change their reflectance level in response to a plurality of drive voltages applied thereto, for controlling the vehicle lighting system and for monitoring a vehicle interior for an automotive vehicle. The system includes a light sensing device and a control circuit formed as a single VLSI CMOS circuit. The light sensing device comprises a photosensor array having a field of view encompassing a vehicle interior. The logic and control circuit determines a background light signal from photosensor element signals generated by the photosensor elements in the photosensor array indicative of light levels incident on the photosensor elements. The circuit also determines a peak light signal in three different zones or sub-arrays of the photosensor array. The zones or sub-arrays may correspond to three mirrors or mirror segments. The peak light signals in each of the zones and a common background light signal are used to determine independent and separate control signals, which are then output to separate mirror drive circuits for independently controlling the reflectance level of the rearview mirror and the left and right side view mirrors, or alternatively the segments of a mirror. The logic and control circuit uses the background light signal to control the vehicle lighting system. The logic and control circuit also determines a vehicle intrusion condition if there is movement within the vehicle in a vehicle intrusion detection mode of the vehicle interior monitoring system. The logic and control circuit also stores image data in memory in the compartment image data storage mode of the vehicle interior monitoring system.

This application is a continuation-in-part of co-pending InternationalPatent Application No. PCT/US94/01954, which designates the UnitedStates and which was filed Feb. 25, 1994 and which is acontinuation-in-part of U.S. patent application Ser. No. 08/023,918,filed Feb. 26, 1993, now U.S. Pat. No. 5,550,677.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an automatic rearview mirror system forautomotive vehicles which automatically changes reflectance level inresponse to glare causing light, and more particularly relates to animproved automatic rearview mirror system using only a rearwardly facingsensor. This invention further relates to an automatic rearview mirrorand vehicle interior monitoring system for automotive vehicles whichalso monitors a vehicle interior or compartment. This invention furtherrelates to an automatic rearview mirror and vehicle interior monitoringsystem for automotive vehicles which may also be used as a vehicleintrusion detection system or as a compartment image data storagesystem. This invention further relates to an automatic rearview mirrorand a vehicle lighting control system using an image sensor, such as aphotosensor array.

2. Description of Related Art

Automatic rearview mirrors and mirror systems have been devised forvarying the reflectance level of a variable reflectance rearview mirrorby reducing the reflectance automatically in response to annoying glarelight, as seen rearwardly of the rearview mirror or mirrors by a driverof the vehicle, and by increasing automatically the reflectance to anormal or maximum reflectance level when the annoying glare lightsubsides. These automatic mirrors have been changed over the years in aneffort to improve their performance characteristics and associated levelof glare protection.

Early automatic rearview mirrors used a rearwardly facing sensor andcontrol circuit to change mirror reflectance. One example of such a"single-sensor" type mirror is described in U.S. Pat. No. 4,266,856. Inthese prior art single-sensor type mirrors, the rear glare light wasincident on a rearwardly facing sensor or photocell, such as aphotodiode, photoresistor or phototransistor. These mirrors sufferedfrom various problems, however, including the problem that these mirrorswould become increasingly sensitive and even "lock-up" in their minimumreflectance level or state as the driver encountered significantlyhigher light levels in town or city driving. This required the driver torepeatedly adjust the mirror's sensitivity control to prevent suchproblems.

To overcome the problems of single-sensor type mirrors, a non-rearwardlyfacing photocell for sensing "ambient" light was added. It was believedthat the desired reflectance necessary to relieve the driver from glaredepended not only on glare light but also on ambient light. Accordingly,these "two-sensor" type mirrors used two separate photocells, onegenerally facing rearwardly and one generally facing forwardly (or othernon-rearwardly facing direction) of the mirror or vehicle. The signalsfrom these two photocells were then compared in some fashion, and when,for example, the glare light from the rear was comparatively high withrespect to the "ambient" light, a control circuit would apply a controlsignal to reduce mirror reflectance. Some examples are described inGerman Laid-Open Patent No. 3,041,692; Japanese Laid-Open Patent No.58-19941; and U.S. Pat. Nos. 3,601,614; 3,612,666; 3,680,951; 3,746,430;4,443,057; 4,580,875; 4,690,508; and 4,917,477. In many of these priorart automatic rearview mirrors, light generally forward of the mirror orvehicle was incident on the second photocell.

These arrangements, however, also had problems. In some of these mirrorsthe forwardly facing or "ambient" light sensor was inaccurate because itdid not correctly measure ambient light levels since it did not includelight generally rearward of the mirror or vehicle. Some examples includethe devices described in U.S. Pat. Nos. 4,443,057 and 4,917,477. Otherprior art devices overcame these deficiencies by providing a controlcircuit which correctly measured ambient light as a combination of boththe forward and rear light levels. Examples of this significantlydifferent approach are described in U.S. Pat. Nos. 4,793,690 and4,886,960.

The prior art two-sensor type systems generally provided improvedperformance over prior art single-sensor type systems but were also morecomplex and costly. In part, this was because using separate forwardlyand rearwardly facing photocells required that the performancecharacteristics of the two separate photocells, such as photoresistors,be matched appropriately to ensure consistent performance under variousoperating conditions. Matching photocells such as photoresistors,however, generally involves complex, expensive and time consumingoperations and procedures.

Both the prior art single-sensor and two-sensor type mirrors presentedadditional problems when they were also used to control the exteriorside view mirrors. This is because such prior art systems used a commoncontrol or drive signal to change the reflectance level of both theinterior rearview mirror and the exterior left and/or right side viewmirrors by substantially the same amount. In U.S. Pat. No. 4,669,826,for example, a single-sensor type mirror system used two rearwardlyfacing photodiodes to control both an interior rearview mirror and theleft and/or right side view mirrors based on the direction of incidentlight from the rear. Another example includes the two-sensor type systemdescribed in U.S. Pat. No. 4,917,477.

In rearview mirror systems, however, each of the interior rearview andexterior side view mirrors may reflect different source light levels.More specifically, the inside rearview mirror, left side view mirror andright side view mirror each enable the driver to view a differentportion or zone of the total rearward area. of course, there may be someoverlap of the image information contained in each of the three zones.The situation is further complicated with multi-lane traffic becauseeach of the mirrors reflects different light levels caused by theheadlights of the vehicles which are following, passing or being passed.As a result, in the prior art systems, when the reflectance level of theinterior rearview mirror was reduced to decrease the glare of headlightsreflected therein, the reflectance level of the exterior left and rightside view mirrors was also reduced by substantially the same amount,even though, for example, the side view mirrors might not be reflectingthe same level of glare light, if any. Accordingly, rear vision in theexterior left and right side view mirrors could be improperly reduced.

Other prior art two-sensor type systems used a common ambient lightsensor and several rearwardly facing sensors, one for each of themirrors. An example is the alternate system also described in U.S. Pat.No. 4,917,477. This approach is not satisfactory, however, because itreduces system reliability and increases complexity and cost.

Finally, some prior anti-glare mirrors used several sensors to controlthe segments of a variable reflectance mirror. One example is disclosedin U.S. Pat. No. 4,632,509, which discloses a single-sensor type mirrorusing three rearwardly facing photocells to control three mirrorsegments depending on the direction of incident light from the rear. Seealso U.S. Pat. No. 4,697,883. These prior mirror systems generally havethe same problems as the other singlesensor type mirrors. Some otheranti-glare mirrors are generally disclosed in U.S. Pat. Nos. 3,986,022;4,614,415; and 4,672,457.

Consequently, there is a need for an automatic rearview mirror systemfor an automotive vehicle having improved reliability and low cost,which accurately determines or otherwise discriminates light levels thatthe driver will experience as glare without the need for a separateforwardly facing photocell. In addition, as noted above, there is also aneed for an automatic rearview mirror system of high reliability and lowcost, which accurately determines light levels that the driver willexperience as glare, and which can control independently the reflectanceof a plurality of mirrors according to the light levels actuallyreflected by each of the rearview and exterior side view mirrors withoutthe need for additional and separate rearwardly facing photocells. Thereis also a need for an automatic rearview mirror system that canindependently control the segments of a variable reflectance mirrorwhile accurately determining light levels that the driver willexperience as glare in each segment of the mirror without the need foradditional and separate forwardly and rearwardly facing photocells.

One concern with automatic rearview mirror systems, as well as othersystems having sensing, control or logic circuits located in therearview mirror, is that differences in vehicle design and mirror fieldof view requirements may result in rearview mirrors having a variety ofappearances (or finishes), forms (or shapes) and sizes. These variationsgenerally require the re-design and re-tooling of a number of thecomponents or sub-assemblies of the rearview mirror head assembly.However, it is generally desirable to reduce the number of components orsub-assemblies of the rearview mirror head assembly so as to reducecost, product development lead time and manufacturing complexity. Toachieve this in automatic rearview mirrors, as well as other systemshaving sensing, control or logic circuits located in the rearviewmirror, it is desirable to locate the sensing, control or logic circuitsand related components in a housing or module, which is attached,connected, made integral with or otherwise associated with the rearviewmirror mounting bracket means or structure so that a common design of amounting bracket sub-assembly for a rearview mirror may be used with avariety of rearview mirror head assemblies.

Vehicle lighting systems may include a variety of vehicle lights,including low intensity peripheral or side lights that allow othervehicle drivers to see the vehicle in lower light conditions, highintensity headlights that operate in a low beam mode or a high beam modefor general night driving, and fog lights that provide low groundlighting with less back scattering to improve the driver's views inadverse weather conditions, such as fog, rain and snow. Vehicle lightingsystems may also include headlights having an intermediate or mid beammode, as well as the low and high beam modes. Vehicle lighting systemsmay also include vehicle running lights, which are vehicle headlightsthat are operated at an appropriate intensity to improve the ability ofother vehicle drivers to see the vehicle during the day. Vehicle runninglights may also be used for lower lighting conditions, such as certainadverse weather conditions or other lower visibility conditions.

Thus, as the number of vehicle lighting options has increased, it hasbecome more complex for the driver to determine the appropriate vehiclelighting configuration and to operate or control the vehicle lightingsystems. Therefore, improved vehicle lighting control systems arerequired that may operate with other systems, such as automatic rearviewmirror systems and vehicle interior monitoring systems, or asstand-alone systems.

Finally, unauthorized vehicle intrusion for the purpose of stealing thevehicle or its contents is a significant problem. Each year, automotivemanufacturers are including vehicle anti-theft or intrusion detectionsystems on more vehicles to deter potential intruders and to prevent thetheft of vehicles or their contents. Currently known vehicle anti-theftsystems are generally designed to protect the vehicle or its contentsfrom theft or vandalism. There are many versions of vehicle anti-theftsystems using various sensor technologies that attempt to deter theft orvandalism using the horn, siren or flashing lights, or other alarmmechanisms to bring attention to a vehicle. As is known, existingintrusion detection systems for vehicles use sensor technologies thathave various limitations, including the problem of false triggering. Forexample, in many cases active vehicle alarms are simply ignored bypeople who assume that the alarm was falsely triggered. Theproliferation of separate automatic rearview mirror systems and vehicleintrusion detection systems is also costly. Therefore, vehicle intrusiondetection systems using an improved sensor technology are required thatoperate in combination with other vehicle systems (such as automaticrearview mirror systems) or that operate independently.

Even with such anti-theft systems, recovered stolen vehicles typicallyprovide little or no evidence of the vehicle thief. Therefore, systemsare required that provide an image of the vehicle thief that would beuseful to law enforcement and the insurance industry as an aid inidentifying the person(s) responsible for the vehicle theft, and thatoperate in combination with other vehicle systems (such as automotiverearview mirror systems) or that operate independently.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome the problems of theprior art.

It is another object of the present invention to provide an automaticrearview mirror system of improved reliability.

It is yet another object of the present invention to provide anautomatic rearview mirror system that accurately determines light levelsthat the driver will experience as glare without the need for a separateforward facing sensor or other non-rearwardly facing photocells.

It is another object of the present invention to provide an automaticrearview mirror system of high reliability that accurately determineslight levels that the driver will experience as glare, and which canindependently control a plurality of mirrors or mirror segmentsaccording to different fields of view without the need for additionaland separate rearwardly facing photocells.

According to one aspect of the present invention, using a photosensorarray and an appropriate control circuit allows the elimination ofseparate forwardly facing or other non-rearwardly facing photocells,thereby allowing for lower costs and increased reliability since it isnot necessary to match two separate photocells such as photoresistors.

According to another aspect, the present invention which achieves one ormore of these objectives relates to a control system for controlling aplurality of variable reflectance mirrors or mirror segments whichchange their reflectance in response to a signal from a drive circuit.The system comprises a plurality of variable reflectance mirrors, aphotosensor array and a control circuit receiving signals from thephotosensor array for controlling the mirrors. The photosensor array ismountable to view rearwardly of the mirror or vehicle. The photosensorarray comprises a plurality of sets of photosensor elementscorresponding to the plurality of variable reflectance mirrors. Thephotosensor elements in each set produce a plurality of photosensorelement signals in response to light incident thereon. The controlcircuit determines control signals, indicative of a desired reflectancefor each of the plurality of variable reflectance mirrors, in responseto receiving photosensor element signals from the photosensor elementset for each view or zone corresponding to the rearview mirror andexterior side view mirrors and also (or alternatively) the mirrorsegments. The control signals control the drive circuit to cause theplurality of variable reflectance mirrors or mirror segments to assumethe desired reflectance.

According to another aspect, the present invention which achieves one ormore of these objectives relates to an automatic rearview mirror systemfor an automotive vehicle comprising at least one variable reflectancerearview mirror, and an array of sensing elements to sense light levelsin an area rearward of the at least one variable reflectance rearviewmirror. Each of the sensing elements is adapted to sense light levels oflight incident thereon and to output an electrical signal indicative ofthe sensed light levels. The system further comprises a signalprocessor, connected to the array of sensing elements, receiving andusing the electrical signals indicative of the sensed light levels fromthe sensing elements to determine a first electrical signal indicativeof a background light level in the area rearward of the at least onevariable reflectance rearview mirror and to determine a secondelectrical signal indicative of at least one peak light level in thearea rearward of the at least one variable reflectance rearview mirror.The signal processor determines at least one control signal indicativeof the desired reflectance level of the at least one variablereflectance rearview mirror from the first electrical signal indicativeof the background light level and the second electrical signalindicative of the at least one peak light level. The system furthercomprises at least one drive circuit connected to the signal processorand to the at least one variable reflectance rearview mirror forreceiving the at least one control signal and generating and applying atleast one drive signal to the at least one variable reflectance rearviewmirror to drive the at least one variable reflectance mirror to thedesired reflectance level.

According to another aspect, the present invention which achieves one ormore of these objectives relates to a control system for controlling aplurality of variable reflectance mirrors, each of which change theirreflectance level in response to a drive signal from an associated drivecircuit, for an automotive vehicle. The system comprises a plurality ofvariable reflectance mirrors, and a photosensor array mountable to facesubstantially towards a rear area. The photosensor array comprises aplurality of photosensor element sets. Each set comprises a plurality ofphotosensor elements. Each of the photosensor elements generates aphotosensor element signal indicative of a light level of light incidentthereon, and each of the sets corresponds to one of the plurality ofvariable reflectance mirrors. The system further comprises a controlcircuit, connected to the photosensor array, for determining andapplying a plurality of control signals. Each of the control signals isindicative of a desired reflectance level for each of the plurality ofvariable reflectance mirrors in response to receiving the photosensorelement signals from each of the plurality of photosensor element sets.The system further comprises a plurality of drive circuits connected tothe control circuit and to different ones of the plurality of variablereflectance mirrors associated therewith. Each of the control signals isoutput to the drive circuit associated therewith, to generate and applya drive signal to each of the plurality of variable reflectance mirrorscausing each of the mirrors to assume a desired reflectance level.

According to another aspect, the present invention which achieves one ormore of these objectives relates to a control system for controlling atleast one variable reflectance mirror for an automotive vehicle. Thesystem comprises photosensor array means for sensing light levels in anarea rearward of the at least one variable reflectance mirror andgenerating photosensor array signals, means for determining a backgroundlight signal from the photosensor array signals, means for determining apeak light signal from the photosensor array signals, and means forcontrolling a reflectance level of the at least one variable reflectancemirror using the background and peak light signals.

According to another aspect, the present invention which achieves one ormore of these objectives relates to a method of controlling thereflectance of at least one variable reflectance mirror comprising thesteps of sensing light levels in an area rearward of the at least onevariable reflectance mirror with an array of sensing elements,determining a background light level from the sensed light levels,determining a peak light level from the sensed light levels, andcontrolling a reflectance level of the at least one variable reflectancemirror using the determined background and peak light levels.

By using a plurality of photosensor element sets or sub-arrays on aphotosensor array to control a plurality of mirrors and also (oralternatively) mirror segments, the mirrors may be controlledindependently to vary their reflectance in accordance with the viewassociated with each of the photosensor element sets or sub-arrays.

According to another aspect the present relates to an automatic rearviewmirror system for an automotive vehicle comprising a variablereflectance rearview mirror, a photosensor array means for sensing lightlevels in an area rearward of said variable reflectance rearview mirrorand for generating photosensor array signals, a signal processing meansfor receiving said photosensor array signals and for determining fromsaid photosensor array signals a signal for controlling said variablereflectance rearview mirror, and a mounting bracket means for attachingsaid variable reflectance rearview mirror to said automotive vehicle,said mounting bracket means further comprising a housing means forhousing said photosensor array means and said signal processing means.

According to another aspect the present relates to a vehicle lightingcontrol system for controlling a vehicle lighting system in anautomotive vehicle comprising a photosensor array means for sensinglight levels in a forward field of view and generating a set ofphotosensor array signals, and a signal processing means coupled to saidphotosensor array means for receiving said set of photosensor arraysignals and determining from said set of photosensor array signals atleast one control signal for controlling said vehicle lighting system.

According to another aspect, the present invention relates to a controlsystem for monitoring a vehicle interior and for controlling at leastone variable reflectance mirror for an automotive vehicle. The systemcomprises photosensor array means for sensing light levels in an arearearward of said photosensor array means and generating at least a firstset of photosensor array signals, first determining means coupled tosaid photosensor array means for receiving said at least a first set ofphotosensor array signals and determining from at least a portion ofsaid at least a first set of photosensor array signals a first signalfor controlling said at least one variable reflectance mirror, seconddetermining means coupled to said photosensor array means for receivingsaid at least a first set of photosensor array signals and determiningat least a first set of values indicative of said at least a portion ofsaid at least a first set of photosensor array signals, and memory meanscoupled to said second determining means for receiving and storing saidat least a portion of said at least a first set of photosensor arraysignals.

According to another aspect, the present invention relates to a vehicleintrusion detection system for detecting movement within a vehicleinterior for an automotive vehicle. The system comprises photosensorarray means for sensing light levels in an area including at least aportion of a vehicle interior and generating at least a first set and asecond set of photosensor array signals, determining means coupled tosaid photosensor array means for receiving said at least a first set anda second set of photosensor array signals and determining at least afirst set and a second set of values indicative of said at least a firstset and a second set of photosensor array signals, and comparing meanscoupled to said determining means for receiving said at least a firstset and a second set of values indicative of said at least a first setand a second set of photosensor array signals and comparing said atleast a first set and a second set of values to generate at least oneoutput control signal indicative of the correlation between said atleast a first set and a second set of values.

According to another aspect, the present invention relates to acompartment image data storage system for an automotive vehicle. Thesystem comprises photosensor array means for sensing light levels in atleast a portion of a vehicle compartment and generating at least a firstset of photosensor array signals, determining means coupled to saidphotosensor array means for receiving said at least a first set ofphotosensor array signals and determining at least a first set of valuesindicative of said at least a first set of photosensor array signals,and memory means coupled to said determining means for receiving andstoring said at least a first set of values indicative of said at leasta first set of photosensor array signals.

These and other objects, advantages and features of the presentinvention will be readily understood and appreciated with reference tothe detailed description of preferred embodiments discussed belowtogether with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a drawing of an automatic rearview mirror of the presentinvention, including an expanded view of a rearwardly facing photosensorarray located in the upper center area of the mirror surface;

FIG. 1B is another drawing of an automatic rearview mirror of thepresent invention, including an expanded view of the rearwardly facingphotosensor array alternatively located in a bezel or chin of themirror;

FIG. 1C is a diagram of an automatic rearview mirror of the presentinvention, in which the photosensor array and logic and control circuitare located in a housing or module that is attached, connected, madeintegral or otherwise associated with the rearview mirror mountingbracket structure;

FIG. 1D is a side sectional view of the automatic rearview mirror ofFIG. 1C;

FIG. 2 is a drawing of an automotive vehicle with the automatic rearviewmirror system of the present invention;

FIG. 2A is an illustrative diagram of a rearward area of a vehicleinterior as viewed by the photosensor elements of the photosensor arrayfor monitoring the vehicle interior;

FIGS. 3A and 3B are illustrative diagrams of a rearward area as viewedby the photosensor elements of the photosensor array;

FIG. 4A is a generalized diagram of a photosensor array PA(N,M) having asub-array S(X);

FIG. 4B is a generalized diagram of the photosensor array PA(N,M) andsub-arrays S(0), S(1), S(2) and S(3);

FIG. 5 is another schematic diagram of the photosensor array commonlylocated on a light sensing and logic circuit;

FIG. 6 is a schematic block diagram of the automatic rearview mirrorsystem;

FIG. 6A is a schematic block diagram of the automatic rearview mirrorand vehicle interior monitoring system;

FIG. 6B is a schematic block diagram of a vehicle lighting controlsystem having a photosensor array that has a forward field of view;

FIG. 7 is a flow chart illustrating the method of the present inventionfor controlling the reflectance of a rearview mirror or mirrors;

FIGS. 8A and 8B are detailed flow charts for steps S150, S160 and S180of FIG. 7;

FIG. 9 is a flow chart of the general logic flow of FIGS. 7, 8A and 8Bfor controlling the reflectance of three mirrors;

FIG. 10 is another schematic block diagram of the automatic rearviewmirror system of the present invention;

FIG. 10A is a schematic block diagram of the automatic rearview mirrorand/or vehicle interior monitoring system of the present invention;

FIG. 11A illustrates the normalized spectral response of the photosensorarray made using a non-epitaxial silicon process;

FIG. 11B illustrates the normalized spectral response of the photosensorarray made using an epitaxial silicon process;

FIG. 12 is a flow chart illustrating the method of the present inventionof the vehicle interior monitoring system;

FIG. 12A is a flow chart illustrating the method of the presentinvention for a vehicle intrusion detection system configuration of thevehicle interior monitoring system of FIG. 12;

FIG. 12B is a flow chart illustrating the method of the presentinvention for the compartment image data storage system configuration ofthe vehicle interior monitoring system of FIG. 12; and

FIGS. 13A, 13B, 13C and 13D are flow charts illustrating the method ofthe present invention for controlling a vehicle lighting system.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

I. The Automatic Rearview Mirror System

FIG. 1A illustrates an automatic rearview mirror 1 comprising a variablereflectance mirror element 1a and a single rearwardly facing photosensor2. The photosensor 2 is mounted facing rearwardly of the rearview mirror1 so that its field of view encompasses an area comprising a rear windowarea and at least a portion of either or both side window areas. Alsoshown is a switch 3 to allow a driver to manually control severalpossible mirror functions, such as an on-off control switch, asensitivity adjustment and a force-to-day or a force-to-night switch(i.e., forced maximum or minimum reflectance levels, respectively). Anexpanded view of the photosensor 2, which is preferably located in anupper center area of the variable reflectance mirror element 1a asshown, shows a light sensing and logic circuit 26 comprising aphotosensor array 32 and a logic and control circuit 34 (which is notshown in FIG. 1A but is shown in FIG. 6 as discussed below). Aphotosensitive surface of each of the photosensor elements 32a (shown inFIG. 5) of the photosensor array 32 senses light levels or imageinformation in a predetermined field of view encompassing an arealocated rearwardly of the rearview mirror 1. A lens 30 images orotherwise focuses the light information from the predetermined field ofview onto the photosensor array 32.

The rearview mirror 1 further comprises a channel mount 1b or othermounting means used to fixedly attach the mirror 1 to the windshield orheadliner area of the vehicle. The rearview mirror 1 is generallyadjustable with respect to the channel mount 1b to allow a driver toposition the mirror for correct viewing of the rearward area or scene sothat the driver's sightline through the rearview mirror 1 is alignedapproximately with the vehicle's centerline.

Preferably, the photosensor 2 is fixedly mounted on the adjustableportion of the rearview mirror 1 as shown in both FIGS. 1A and 1B sothat the viewing axis of the photosensor 2 is generally aligned with theviewing axis of the mirror 1 which is perpendicular to the glass surfaceof the mirror 1. This approach is preferable both because of packagingconcerns and because it provides a guaranteed sightline. It is, however,within the scope of the present invention to mount the photosensor array32 so that it is movable with respect to the variable reflectance mirrorelement 1a of the rearview mirror 1.

More preferably, as shown in FIG. 1A, the photosensor 2 is located inthe upper center area of the variable reflectance mirror element 1a.This may be required, for example, if it is necessary to reduce thebezel size of the rearview mirror 1. If the photosensor 2 is locatedbehind a glass surface of the variable reflectance mirror element 1a, anappropriately sized hole is provided in the protective and reflectivematerials of the variable reflectance mirror element 1a. Additionally, acorresponding area within an active layer of the variable reflectancemirror element 1a may be removed or otherwise rendered inactive toenable the photosensor 2 to view directly the rearward scene.Alternatively, for manufacturing reasons, the photosensor 2 may view therearward scene through the active layer of the variable reflectancemirror element 1a, in which case it is preferable to compensate for orotherwise negate the effects of reducing reflectance and correspondinglythe transmittance of the variable reflectance mirror element 1a so thatthe photosensor 2 effectively views the rearward scene directly as willbe described later.

Most preferably, a reflective surface is maintained within the hole toboth preserve the cosmetic appearance of the assembly as viewed by thedriver and to maximize the reflective surface. This can be achieved byproviding a very thin metal reflective layer (100 Å thickness or lower)of aluminum, stainless steel, chromium, or silver, etc., so as to besufficiently transmitting for incident light to enable proper operationof the photosensor array 32 but also sufficiently reflective to appearmirror-like in the area of the hole. Alternatively, a reflective tape,which is both sufficiently transmitting and reflective to achieve theobjectives described herein, may be adhered at the hole region usingsuitable means such as an optical adhesive and the photosensor array 32may then be mounted behind the optical adhesive. Additionally, thin filmstacks such as a solid state tri-layer of 1/4 wave TiO₂, 1/4 wave SiO₂and 1/4 wave TiO₂ or some other single thin film of a high indexmaterial may be mounted behind or coated upon the area of the hole.Finally, since the preferred photosensor array 32 is responsive to bothvisible light and near infrared, it is preferable to select a materialwhich reflects a significant proportion of visible light while beingessentially transparent to infrared.

As shown in FIG. 1B, the photosensor 2 may also be located in the bezelor chin of the rearview mirror 1 to view the rearward area directlywithout any compensation. In another preferred embodiment, thephotosensor 2 may also be located on or near the channel mount ormounting bracket 1b so that the axis of the photosensor 2, which isperpendicular to the plane of the photosensor array 32, is in fixedalignment with the vehicle's centerline regardless of the adjustedposition of the rearview mirror 1.

In particular, as shown in FIGS. 1C and 1D, a sensing and logic circuitassembly 27, which comprises a sensing and logic circuit 26 and thephotosensor 2 and switch 3 on a printed circuit board, is located in ahousing or module 7 that is attached, connected, made integral orotherwise associated with the rearview mirror 1. In the embodiment shownin FIGS. 1C and 1D, a mounting bracket 6 is fixed relative to theheadliner area of the vehicle body in a header mount arrangement; and arearview mirror head assembly 1h is adjusted by a spherical pivot 6d atthe interface of the mounting bracket 6 and the rearview mirror headassembly 1h. The mounting bracket 6 may also be releasably attached to amounting button (not shown) that is attached to the windshield toprovide generally improved ease of assembly and replacement, as well assafety. Alternatively, the mounting bracket 6 may be attached to thewindshield or headliner area of the vehicle by any of the various meanswell known to those skilled in the art.

In particular, the mounting bracket 6 comprises a retaining spring 6a, aretaining screw 6b, a wire harness opening 6c for receiving a wireharness assembly 8, and a spherical pivot 6d having an opening for wires6e that are used to control the variable reflectance mirror element 1a.The housing or module 7 comprises a retaining housing or module 7a forpartially mounting the sensing and logic circuit assembly 27, a rearhousing or module cover 7b, a heat sink 7c for the sensing and logiccircuit assembly 27, a screw 7d for securing the heat sink 7c to themirror bracket 6, and a wire connector 7e for connecting the harnessassembly 8 and wires 6e to the sensing and control circuit assembly 27.The harness assembly 8 is used, in part, to supply power to the sensingand logic circuit assembly 27.

Also, as shown in FIGS. 1C and 1D, the automatic rearview mirror 1comprises the variable reflectance mirror element 1a, a mirror cushionsupport 1c, an impact absorber layer 1d, a bezel 1e, a mirror case ifand clamp springs 1g for receiving and securing the spherical pivot 6dof the mounting bracket 6.

For other vehicles, such as trucks, the photosensor 2 may also belocated with each of the external side view mirrors as will be describedlater.

The lens 30 is preferably a single molded plastic lens approximately 2millimeters in diameter and is preferably bonded to or in close contactwith the photosensor array 32. The lens 30 may, however, include anyappropriate image focusing means such as conventional single componentoptics, holographic lens type optics, binary optics or a microlens. Thelens 30 preferably is also designed to focus an image of the rearwardscene within a field of view defined by a cone. The cone's centerline isperpendicular to the plane of the photosensor array 32 and the conepreferably has an included angle of approximately 100 degrees. Thus, theimage is focused onto a circular area of the plane of the photosensorarray 32. Of course, the photosensor array 32 could be positioned inother than a rearwardly facing direction so long as appropriate lensesor other optics are used to direct the light or image information fromthe rearward area onto the photosensitive surface of the photosensorarray 32.

The pre-positioning of the photosensor array 32 in the rearview mirror 1depends on whether the automatic rearview mirror system 20 is being usedin a left hand or a right hand drive vehicle. In either case, thephotosensor array 32 is preferably pre-positioned within the circulararea of the focused image so that for either a left or right hand drivevehicle and with only driver adjustment of the rearview mirror 1, therearward scene imaged onto the photosensitive surface of the photosensorarray 32 includes the rear window area and at least a portion of theleft and right side window areas of the vehicle.

If a sufficiently large photosensor array 32 is used, then thepre-positioning of the photosensor array 32 is not vehicle specific asdescribed above, and a system 20 using a larger photosensor array 32 maybe used for both left and right hand drive vehicles. The largerphotosensor array 32 is positioned symmetrically within the circulararea of the focused image described above. Using the larger photosensorarray 32 involves using a pattern recognition means to determine theapproximate vehicle centerline so that the appropriate portion of thelarger photosensor array 32 may be selected depending on whether theautomatic rearview mirror system 20 is installed in a left or right handdrive vehicle.

FIG. 2 illustrates an automatic rearview mirror system 20 for anautomotive vehicle, comprising the rearview mirror 1, a left side viewmirror 4 and a right side view mirror 5. As will be discussed below,either or both of the side view mirrors 4 and 5 may be connected to acontrol circuit of the rearview mirror 1. The mirrors 1, 4 and 5 may beconstructed according to any of the methods known to those skilled inthe art and are generally constructed according to the stylingpreferences and specifications of the automotive vehicle manufacturers.The means for mounting the rearview mirror 1, such as the channel mount1b, and the electrical connectors used to connect the mirrors 4 and 5 tothe control circuit of the rearview mirror 1 and the vehicle'selectrical system may include any one of the many configurations knownto those having ordinary skill in the art. The variable reflectancemirror element 1a of the mirrors 1, 4 and 5 may be any device havingmore than one reflectance level corresponding to a specific control ordrive signal. Preferably, however, the variable reflectance mirrorelement 1a is an electrochromic mirror.

As discussed, the photosensor 2 is mounted facing rearwardly of therearview mirror 1 so that its field of view encompasses an areacomprising the rear window area and at least a portion of both the leftside window area and the right side window area. The horizontal andvertical fields of view of the rearward area as seen by the photosensor2, and more particularly by the photosensor array 32, are illustrativelyshown in FIGS. 3A and 3B.

As shown in FIG. 3A, the photosensor array 32 senses a field of viewdivided into three separate zones: a center zone a, a left zone b(generally corresponding to the left side window area) and a right zonec (generally corresponding to the right side window area). Each zone issensed by a separate set or sub-array S(X) of photosensor elements 32a(described with respect to FIGS. 4A and 4B) within the photosensor array32. The center zone, zone a, generally receives light from the rearwindow area of the vehicle. This rear window area is depicted by atrapezoidally shaped rear window figure superimposed on a first set orsub-array S(1) of photosensor elements 32a used to sense light levels inzone a. Zone b includes light from at least a portion of a left sidewindow area. This is depicted by a trapezoidally shaped left rear sidewindow figure and a partially shown left front side window figuresuperimposed on a second set or sub-array S(2) of photosensor elements32a used to sense light levels in zone b. Similarly, zone c includeslight from at least a portion of a right side window area. This isdepicted by a trapezoidally shaped right rear side window figure and apartially shown right front side window figure superimposed on a thirdset or sub-array S(3) of photosensor elements 32a used to sense lightlevels in zone c. Additionally, all three zones include light reflectedfrom whatever fixed body work and interior trim, head rests, vehicleoccupants or other objects that are within the zones a, b and c.

Also as illustratively shown in FIG. 3A, the photosensor elements 32a incolumns 1 to 4 comprise the third photosensor element set in zone c, thephotosensor elements 32a in columns 6-11 comprise the first photosensorelement set in zone a and the photosensor elements 32a in columns 13 to16 comprise the second photosensor element set in zone b. Null zones areprovided between the zones a and b and between the zones a and c toallow for driver adjustment of the rearview mirror 1. These null zonesalso ensure that the center zone a does not include light or other imageinformation from the side window areas of zones b and c.

As will be discussed in more detail below, the logic and control circuit34 selects photosensor element signals from the first photosensorelement set or sub-array S(1) (shown in FIG. 4B) corresponding to zone ato control the reflectance level of the rearview mirror 1. Similarly,the control circuit 34 selects photosensor element signals from thesecond photosensor element set or sub-array S(2) (shown in FIG. 4B)corresponding to zone b to control the reflectance level of the leftside view mirror 4, and further selects photosensor element signals fromthe third photosensor element set or sub-array S(3) (shown in FIG. 4B)corresponding to zone c to control the reflectance level of the rightside view mirror 5. Additionally, for a variable reflectance mirrorelement 1a having segments, such as a center, left and right segment,appropriately defined zones a, b and c, i.e., sub-arrays S(1), S(2) andS(3), corresponding to the mirror segments may be used by the logic andcontrol circuit 34 to control independently the individual mirrorsegments.

FIG. 3B illustratively shows the preferred embodiment for the zones ofthe photosensor array 32. In this embodiment, the logic and controlcircuit 34 selects photosensor element signals from three overlappingsets or sub-arrays S(1), S(2) and S(3) of photosensor elements 32acorresponding to the three overlapping zones a, b and c to control,respectively, the reflectance level of the mirrors 1, 4 and 5. Morespecifically, the control circuit 34 selects photosensor element signalsfrom the photosensor elements 32a in columns 6 to 11 (zone a) to controlthe reflectance level of the rearview mirror 1. The control circuit 34also selects photosensor element signals from photosensor elements 32ain columns 10 to 14 (zone b) to control the reflectance level of theleft side view mirror 4, and further selects photosensor element signalsfrom photosensor elements 32a in columns 3 to 7 (zone c) to control thereflectance level of the right side view mirror 5.

Additionally, in the FIG. 3B embodiment, the lens 30 focuses or imageslight information from: (1) the rear window area onto zone a; (2) atleast a portion of the rear window and left side window areas onto zoneb; and (3) at least a portion of the rear window and right side windowareas onto zone c. Contrastingly, in the FIG. 3A embodiment, the lens 30focuses light from: (1) the rear window area onto zone a; (2) the leftside window area onto zone b; and (3) the right side window area ontozone c. The overlapping zones in the FIG. 3B embodiment are advantageousbecause each set of overlapping photosensor elements 32a in zones a andb and each set of overlapping photosensor elements 32a in zones a and c,as well as the logic and control circuit 34, is able to "preview" thelight information that may, for example, first appear in the rear windowarea (and correspondingly in the rearview mirror 1), but which mayappear shortly thereafter in the left or right side view mirrors 4 and5. By examining at least a portion of the rear window area, theautomatic rearview mirror system 20 is able to more quickly respond toannoying glare light from approaching vehicles or other sources.Overlapping zones are also generally preferred because a glare lightsource located in a common or overlapping area of the rearview mirror 1and one of the side view mirrors 4 or 5 can influence both mirrors.

II. The Light Sensing Device

The light sensing device of the light sensing and logic circuit 26 ispreferably the photosensor array 32 shown in FIG. 5. The photosensorarray 32 has sufficient resolution to view the real image of a scene butmay also use a spatial distribution of light intensities as anapproximation of the imaged scene. An example of such a photosensorarray 32 is the VLSI Vision Limited (VVL) Single Chip Video Camera Model#ASIS 1011.

Since a photosensor array 32 of the type described, namely the VVLSingle Chip Video Camera, is capable of providing image informationhaving sufficient resolution for displaying an actual image or for someother purpose, it will be readily understood that additional features orfunctions may be incorporated by adding circuitry to provide videooutput from the photosensor array 32 in addition to the primary controlfunctions described herein. For example, the video output may be outputto a CRT, flat LC panel display or other appropriate display device,located within the vehicle, to provide a display of the imaged scene forviewing by the driver.

The photosensor array 32 may be located in any of the mirrors 28 or inany other appropriate location, whether local or remote, such as on thevehicle's rear bumper, thereby extending significantly the effectivefield of view normally available to the driver either directly orthrough the vehicle's mirrors 28. Additionally, the photosensor array 32may even replace one or more of the side view mirrors 4 and 5 of theautomatic rearview mirror system 20, thereby reducing the aerodynamicdrag on the vehicle while providing sufficient information to the drivercomparable to that available through the side view mirrors 4 and 5.

A video signal from the photosensor array 32 may also be used by thelogic and control circuit 34 to determine the presence of a vehicle orother object within the field of view of the photosensor array 32 toprovide a visual signal warning such as through a display panel, or evenan audible warning, based on certain parameters, such as distance andspeed of the object. Additionally, if the photosensor array 32 islocated in the rearview mirror 1, the video signal may be used tomonitor the vehicle's interior to detect unauthorized intrusion into thevehicle. This may be achieved by providing electrical power to themirror's logic and control circuit 34 from a vehicle power supply and byactivating a vehicle intrusion monitoring mode when a signal indicatesthat the vehicle's door and trunk locks have been activated. The logicand control circuit 34 may be used to continuously monitor the imagefrom the vehicle's interior thereby allowing detection of objects orpersons moving within the vehicle, and if movement is detected, anothersignal from the logic and control circuit 34 may then activate anintrusion alarm.

Thus, the photosensor array 32 may be used to monitor the vehicleinterior or compartment in a vehicle interior monitoring system. Thismonitoring capability may be used in a vehicle intrusion detectionsystem or in a compartment image data storage system, either incombination with the automatic rearview mirror system or as anindependent system. Using the photosensor array 32 to monitor thevehicle interior to detect potential intruders provides an effectivevehicle intrusion detection system. In an automatic rearview mirror andvehicle intrusion detection system, the photosensor array 32 in therearview mirror 1 provides a good location for monitoring the vehicleinterior because the rearview mirror 1 is: (1) centrally located alongthe vehicle axis; (2) forward of the front seat; and (3) relatively highin the vehicle interior. This location is sufficiently high and farforward so as to provide a very good view of the vehicle interior,including the front and rear seat areas, front and rear door areas andhatchback or rear cargo door areas. The photosensor array 32 may also bepositioned in other locations, including the headliner and headlinerconsole areas, for example, or any other appropriate location dependingon the particular application.

As is discussed later, when the vehicle interior monitoring system isused as a vehicle intrusion detection system, the logic and controlcircuit 34 processes image data to detect motion or movement in thevehicle interior, establishes an intrusion condition if such motion isdetected and outputs one or more control signals to vehicle hardware orto a vehicle controller system. Vehicles today are often equipped withsuch controller systems. These vehicle controller systems may be used tocontrol the exterior lights, interior lights, horn (or siren), ignitionor other such vehicle hardware. The logic and control circuit 34therefore outputs one or more control signals to various vehiclehardware or to the vehicle controller system to activate the interiorand exterior lights, horn or siren or to disable the ignition to deterintruders from stealing the vehicle or its contents. Other controloutput signals may activate RF beacon devices or similar devices withinthe vehicle so that the vehicle may be tracked, as will be furtherdescribed later.

It is, however, within the scope of the present invention for the lightsensing device to comprise any similarly appropriate image or arraysensor. When the light sensing and logic circuit 26 is formed as avery-large-scale-integrated (VLSI)complementary-metal-oxide-semiconductor (CMOS) device, as is known tothose skilled in the art, the light sensing device will share a commonsemiconductor substrate with the logic and control circuit 34.

Preferably, for the described three mirror system, the photosensor array32 comprises a plurality of photosensor elements 32a arranged in 160columns and 40 rows (a 160×40 array) providing a horizontal field ofview of approximately 100 degrees and a vertical field of view ofapproximately 30 degrees. As discussed, FIGS. 3A and 3B illustrativelyshow a 16×4 photosensor array 32. The photosensor array 32 may, however,comprise any appropriately sized array having an appropriate field ofview. For example, the field of view may be narrower when controllingthe segments of only one mirror. Each photosensor element 32a ispreferably about 10 microns square.

As shown in FIG. 4A, the photosensor array 32 generally comprises aplurality of photosensor elements 32a arranged in a photosensor arrayPA(N,M) having N rows of M columns. When viewing the photosensitivesurface of the photosensor array PA(N,M) in a vertical plane, the lowerrow is row 1, the top row is row N, the left hand column is column 1,and the right hand column is column M. A specific photosensor element isidentified as E(n,m) and the signal indicative of a light level incidentthereon is L(n,m). Also, the sub-array S(X), where X=0, 1, 2, . . . , Z,is a rectangular array having P(X) rows of Q(X) columns of photosensorelements 32a and is located such that its lower left hand element isphotosensor element E(T(X) ,U(X)).

As shown in FIG. 4B, a background sub-array S(X) designated S(0) is usedto determine a general background light level B. Signals from thephotosensor elements 32a of each peak sub-array S(X), designated S(1),S(2), . . . , S(Z), are used to determine a peak light level P(z)incident on each peak sub-array S(1), S(2), . . . , S(Z). The generalbackground light level B for background sub-array S(0) and the peaklight level P(z) for each peak sub-array S(X) are then used to determinea mirror control signal V_(c) (z) for controlling at least one mirror ormirror segments associated with each zone.

FIG. 5 generally illustrates a logic layout of the photosensor array 32.The logic and control circuit 34 generates array control signals tocontrol the photosensor array 32. As is well known in the art, thephotosensor array 32 is typically accessed in scan-line format, with thearray 32 being read as consecutive rows, and within each row asconsecutive columns or pixels. Each photosensor element 32a is connectedto a common word-line 33e. To access the photosensor array 32, avertical shift register 33a generates word-line signals for eachword-line 33e to enable each row of photosensor elements 32a. Eachcolumn of photosensor elements 32a is connected to a bit-line 33f whichis connected to a charge-to-voltage amplifier 33c. As each word-line 33eis accessed, a horizontal shift register 33b uses a line 33g to outputthe bit-line signals on consecutive bit-lines 33f to an output line 33hconnected to the logic and control circuit 34. Also shown is a voltageamplifier 33d used to amplify the resulting analog photosensor elementsignals. The analog photosensor element signals are then output on line33h to the analog-to-digital converter 44 and converted to digitalphotosensor element signals.

As discussed above, the photosensor array 32 is responsive to or sensesboth visible light and near infrared illumination. FIGS. 11A and 11Billustrate the normalized spectral response for two versions of thepreferred photosensor array 32. In FIGS. 11A and 11B, visible lightgenerally covers the wavelengths from about 400 nm to about 750 nm,while near infrared illumination or light generally covers thewavelengths from about 750 nm to about 3000 nm (not shown). Moreparticularly, FIG. 11A illustrates the normalized spectral response ofthe preferred photosensor array 32 made using a non-epitaxial siliconprocess, where the peak spectral response occurs at about 800 nm. FIG.11B shows the normalized spectral response of the preferred photosensorarray 32 made using an epitaxial silicon process, where the peakspectral response occurs at about 650 nm. As shown, the non-epitaxialsilicon photosensor array is more sensitive to near infraredillumination having wavelengths on the order of about 800 nm. Thephotosensor array 32 made using the non-epitaxial silicon process andhaving the normalized spectral response of FIG. 11A is most preferred inboth the particular automatic rearview mirror and vehicle interiormonitoring systems described herein. For automatic rearview mirrorsystems as described herein, this is because vehicle headlightsgenerally provide significant levels of near infrared illumination. Forvehicle interior monitoring systems as described herein, either naturalsources (such as sunlight) or supplemental sources of near infraredillumination may be used to enhance the image information available toand the performance of such systems, as will be further discussed below.

The field of view and resolution of the photosensor array 32 depends onthe number and physical dimensions of the photosensor elements 32a andon the design or geometry of the lens 30. For the lens type illustratedin FIG. 1A, the lens 30 may, for example, be designed to have anincluded angle on the order of up to about 140°. For the automaticrearview mirror system previously described, the effective field of viewof approximately 100° horizontal and approximately 30° vertical ispreferred. For the automatic rearview mirror and vehicle interiormonitoring system described herein, an effective field of view ofapproximately 100° horizontal and approximately 75° vertical ispreferred. Also as discussed for the automatic rearview mirror system,the lens 30 preferably focuses an image within a field of view definedby a cone having an included angle of approximately 100 degrees.Accordingly, when the lens 30 focuses the image onto the focal plane ofthe 160×40 photosensor array 32, the photosensor array 32 only fallswithin a segment of the focused image area.

FIG. 2A generally illustrates a view of a vehicle interior 100 (whichincludes the window areas of FIGS. 3A and 3B) as focused by the lens 30and as viewed by a 160×120 photosensor array 32. Also shown are a driveror left seat 101, a front passenger or right seat 102, a rear windowarea 103a, a right side window area 103b and a left side window area103c. The 160×40 photosensor array 32, however, only sees a portion orsegment of the vehicle interior 100, as is shown in FIGS. 3A and 3B. Ina dedicated automatic rearview mirror system, the 160×40 sized array isgenerally preferred since it provides sufficient image information forproviding effective automatic rearview mirror control and because itreduces the cost of the photosensor array 32. If the photosensor array32 is also used to monitor the vehicle interior 100 (or for otherapplications) as is described herein, then the larger 160×120 array sizemay be used to view the vehicle interior 100 as is generally illustratedin FIG. 2A.

Finally, it should be understood that the spatial resolution of thephotosensor array 32 may also be increased. This may be done by makingthe photosensor elements 32a smaller so as to increase the number ofphotosensor elements 32a in a photosensor array 32 having the samephysical dimensions. Additionally, spatial resolution may be increasedby varying the lens 30 to decrease the included angle of the image coneso that the photosensor array 32 views a smaller portion of an image onthe vehicle interior 100.

In summary, the array size of the photosensor array 32 and the numberand physical dimensions of the size of the photosensor elements 32a andthe lens design or geometry of lens 30 may all be varied to optimize theeffective field of view of the photosensor array 32 depending on theapplication.

As is discussed later, an exposure time or exposure period EP of thephotosensor array 32 may be varied over some range depending on thelight level. Thus, the value of EP is increased for decreasing lightlevels and approaches a maximum for low light levels, and it isdecreased for increasing light levels and approaches a minimum for highlight levels. For a given value EP_(v) of the exposure period, there isa light level LL_(MIN) that is sufficiently distinct from low signalnoise in the photosensor element signal L(n,m) of each photosensorelement E(n,m) so that it may be accurately sensed, and there is also alight level LL_(MAX) for which the photosensor element signal L(n,m) ofeach photosensor element E(n,m) is a maximum. The ratio of LL_(MAX)/LL_(MIN) at EP_(v) may be used to represent a dynamic range of DR(n,m)in decibel (dB) units of each photosensor element E(n,m), whereDR(dB)=10 LOG (LL_(MAX) /LL_(MIN)). The image data is preferablyoptimized such that it is approximately centered within the dynamicrange DR(N,M) of the photosensor array 32. This may be done bydetermining an array response AR of RA(N,M), which is described later,where the minimum and maximum digital values of AR correspond to theminimum and maximum digital values possible for Val RA(n,m) (e.g., 0 and255 for 8-bit data resolution). The exposure period is varied oradjusted until AR approaches the center or mid-point of the possibledata value range (e.g., 127 for 8-bit data resolution).

Since there is a minimum photosensor element signal that may beaccurately measured, a supplemental source of illumination may bedesirable or necessary to enhance the effective sensing capabilities ofthe photosensor array 32 by providing supplemental source illuminationSSI. Although the photosensor array 32 is able to monitor the vehicleinterior 100 over a range of background lighting levels from about 0.1lux (a dark garage) to about 30-60K lux (a bright, sunny day), usingeither visible or near infrared SSI to illuminate the vehicle interior100 generally (or specific areas therein) significantly enhances theeffectiveness or performance of the photosensor array 32 in variousapplications. Also, SSI is preferably provided only during the exposureperiod EP of the photosensor array 32 rather than continuously. PulsedSSI reduces power consumption, extends the life of the supplementalsource of illumination and provides generally higher instantaneousillumination than may be provided by continuous illumination. Also,pulsed infrared SSI is generally more difficult to detect by infraredillumination sensing apparatus that may be used by potential intruders.

For the specific vehicle interior monitoring system applicationsdescribed herein, near infrared illumination between about 700 and 1200nm is preferred because: (1) it is visible to the photosensor array 32but not to the human eye (see FIGS. 11A and 11B); and (2) it does notaffect adaption of the human eye. There are a number of readilyavailable near infrared illumination sources, including solid-statesources such as light emitting diodes (LEDs) and lasers, flash lampssuch as xenon or krypton lamps, incandescent lamps such as tungstenlamps, as well as many others. Preferred, however, are gallium arsenide(GaAs) or gallium aluminum arsenide (GaAlAs) LEDs because they provide arelatively narrow band (about 750 to 950 nm) of near infraredillumination (see FIGS. 11A and 11B). Such illumination sources are alsotypically packaged with a lens to distribute the illumination. Dependingon the particular application, the illumination distributioncharacteristics of readily available lens/source packages may range fromnarrow so as to provide spot or collimated illumination to very diffuseso as to cover about 160°. In the vehicle interior monitoring systemdescribed herein, the lens/source package preferably providesillumination coverage on the order of about 100°.

Other illumination sources providing broad-band illumination(ultraviolet through infrared) may also be used, but it may be desirableor necessary to filter such broad-band illumination using absorption orinterference type filters, or any other appropriate filter. Inparticular, an interference filter known as a long-wave pass filter orcold mirror reflects visible light, transmits infrared illumination andlooks like the normal silvered mirrors typically used in the rearviewmirror 1. Unlike cold mirrors, however, silvered mirrors reflect nearinfrared illumination. Since the cold mirror resembles the silveredmirror in the rearview mirror 1, it may be used to replace a section oreven all of the silvered mirror. In particular, the supplemental sourceof illumination may be located behind the cold mirror element andadjacent to the photosensor array 32 with an opaque barrier separatingthe two to prevent supplemental illumination reflections within therearview mirror 1 from directly affecting the photosensor array 32.

Alternatively, a long-wave pass absorption filter may be used with asupplemental source of broad-band infrared illumination. Long-wave passabsorption filters may be fabricated using a wide variety of polymershaving appropriate optical transmission characteristics such as epoxies,acrylics, polycarbonates, as well as a variety of glasses. The acrylicand polycarbonate polymers are preferred because they areenvironmentally stable, cost effective and because they may be used toinjection mold parts having various geometric shapes or polished ortextured surfaces. Using absorption filter materials, the photosensorarray 32 and supplemental source of illumination may be integrated intothe rearview mirror 1 or elsewhere within or on the vehicle so that theyare not readily apparent to vehicle occupants, passers-by or potentialintruders.

III. The Logic And Control Circuit

FIG. 6 shows the light sensing and logic circuit 26 comprising thephotosensor array 32 and the logic and control circuit 34. The logic andcontrol circuit 34 comprises a logic circuit 46, a clock 47, arandom-access-memory (RAM) 50, or other appropriate memory, and adigital-to-analog converter 52. The logic circuit 46 is preferably adedicated configuration of digital logic elements constructed on thesame semiconductor substrate as the photosensor array 32. Alternatively,the logic circuit 46 may also be a microprocessor comprising a centralprocessing unit (CPU) and a read-only-memory (ROM). The logic circuit 46may also be implemented using gate array technology or any otherappropriate hardwired logic circuit technology.

The logic circuit 46 interfaces with the clock 47, provides arraycontrol signals to the photosensor array 32, manages data flow to andfrom the RAM 50 and converters 44 and 52, and performs all computationsfor determining a digital mirror control signal V_(DAC) (Z) for causingthe variable reflectance mirror element 1a to assume a desiredreflectance level. As discussed, the analog-to-digital converter 44converts the analog photosensor element signals to the digitalphotosensor element signals processed by the logic circuit 46. It hasbeen found that an eight-bit analog-to-digital converter 44 providesadequate data resolution for controlling the mirrors 1, 4 and 5.Preferably, the analog-to-digital converter 44 is constructed on thesame semiconductor substrate as the photosensor array 32 as shown inFIG. 5.

The digital photosensor element signals output to the logic and controlcircuit 34 are generally stored in the RAM 50 for processing. The valuesof the digital photosensor element signals for the photosensor arrayPA(N,M) are correspondingly stored in an array in the RAM 50 designatedRA(N,M). The logic circuit 46 processes the values of each of thedigital photosensor element signals, which are designated Val RA(n,m),to determine an instantaneous or substantially real-time backgroundlight signal B_(t) for a time period t and at least one peak lightsignal P(z). The logic circuit 46 uses these signals, which may also betemporarily stored in the RAM 50, to determine a digital control signalV_(DAC) (z) to cause at least one mirror or mirror segment to assume adesired reflectance level. The digital mirror control signal V_(DAC) (z)is then output to the digital-to-analog converter 52, which outputs acorresponding analog mirror control signal V_(C) (z) to a mirror drivecircuit 24. Alternatively, the digital-to-analog converter 52 need notbe used if the logic circuit 46 generates a pulse-width-modulated (PWM)mirror control signal to control the mirror drive circuit 24.

The mirror drive circuit 24 comprises mirror drive circuits 24a, 24b and24c. The drive circuit 24 drives mirrors 28, which comprises a rearviewmirror 28a (mirror A), a left side view mirror 28b (mirror B) and aright side view mirror 28c (mirror C). Mirrors A, B and C correspond,respectively, to the rearview mirror 1, the left side view mirror 4 andthe right side view mirror 5 shown in FIG. 2. It is, of course, withinthe scope of the present invention for the mirror A to be a mirror otherthan the rearview mirror 1. It is similarly within the scope of thepresent invention for the mirror B to be a mirror other than the leftside view mirror 4, and for the mirror C to be a mirror other than theright side view mirror 5. It is also within the scope of the inventionfor the mirrors A, B and C to be mirror segments or zones of thevariable reflectance mirror element 1a where the peak sub-array S(X) foreach zone corresponds to a segment of the variable reflectance mirrorelement 1a. Thus, for example, S(1) may correspond to a center mirrorsegment, S(2) may correspond to a left mirror segment and S(3) maycorrespond to a right mirror segment. Any other appropriate mirrorsegmentation scheme may also be used.

A sensitivity control circuit 42 is used to input a sensitivity signal Sto the logic and control circuit 34. In addition, signals from aforce-to-day (maximum reflectance) switch 36, a reverse-inhibit (maximumreflectance) switch 38 and a force-to-night (minimum reflectance) switch40 may also be input to the logic and control circuit 34. The switch 3of FIGS. 1A and 1B may include the sensitivity control circuit 42, aswell as the force-to-day switch 36 and the force-to-night switch 40.

The switches 36, 38 and 40 each generate a signal causing the logiccircuit 46 to override its normal operation, as will be described withrespect to FIGS. 7, 8A and 8B, and to output mirror control signalsV_(c) (z) to the mirror drive circuit 24 causing the variablereflectance mirror 28 to assume a maximum or minimum reflectance levelin accordance with the appropriate signals from the switches 36, 38 or40.

Finally, the logic and control circuit 34 may also be used to control avehicle lighting switch 45 to automatically turn on and off a vehicle'sheadlights and sidelights. This feature will be further described later.

FIG. 6A shows the block schematic diagram of the automatic rearviewmirror and vehicle interior monitoring system. The previous descriptionof FIG. 6 applies here except as follows. First, the logic and controlcircuit 34 includes an analog-to-digital converter 55 for converting oneor more analog control input signals 70 (1, 2, . . . , N; blocks 70a to70n) to digital signals that are input to the logic circuit 46.

With respect to the automatic rearview mirror system, the analog controlinput signals 70 may include any analog control input signal usedtherein, including, for example, analog versions of the control inputsignals provided by the force-to-day-switch 36, reverse-inhibit-switch38, force-to-night-switch 40 or sensitivity control circuit 42 of FIG.6. Of course, digital versions of these same control input signals mayalso be input to the logic circuit 46 as digital control input signals75 (1, 2, . . . , N; blocks 75a to 75n). The analog control outputsignals 80 (1, 2, . . ., N; blocks 80a to 80n) may include any analogcontrol output signal used in the automatic rearview mirror system,including the analog mirror control signals V_(c) (z). The analogcircuits/switches 81 (1, 2, . . . , N; blocks 81a to 81n) may includethe drive mirror circuits 24 that are used to drive the variablereflectance mirrors 28. As discussed with respect to FIG. 6, the analogmirror control signal V_(c) (z) is output to the mirror drive circuit 24causing the variable reflectance mirror 28 to change reflectance levels.Of course, digital control output signals 85 (1, 2, N; blocks 85a to85n) may also be output to digital circuits/switches 86 (1, 2, . . . ,N; blocks 86a to 86n) to the extent that the control output signals aredigital and not analog.

With respect to the vehicle interior monitoring system configured as avehicle intrusion detection system, analog control input signals 70 anddigital control input signals 75 may include, respectively, analog anddigital versions of control input signals used to "arm" or "alert" thevehicle intrusion detection system, as will be further described later.The analog control output signals 80 may include any analog controlsignals output to analog circuits/switches 81 that are used in the abovesystem, including analog circuits or switches used to actuate variousvehicle hardware, such as the vehicle horn (or siren), exterior andinterior lights or ignition control devices. Of course, digital controloutput signals 85 (1, 2, . . . , N; blocks 85a to 85n) may also beoutput to digital circuits/switches 86 (1, 2, . . . , N; blocks 86a to86n) to the extent that the control output signals are digital and notanalog. In particular, the digital control output signal 85 may includea digital word provided to a digital circuit/switch 86 that is a vehiclecontroller system that interfaces with such vehicle hardware.

When the vehicle interior monitoring system is configured as acompartment image data storage system, a nonvolatile memory 57, as shownin FIG. 6A, is included. The nonvolatile memory 57 interfaces with thelogic circuit 46. The nonvolatile memory 57 is used to store image data,as will be further described later. The nonvolatile memory 57 may be anEEPROM or other appropriate nonvolatile memory. An access/securitydecoding logic circuit 58 interfaces with a data access port 59 and thelogic circuit 46. The access/security decoding logic circuit 58 and dataaccess port 59 are used to access the image data stored in thenonvolatile memory 57, as will be further described later. Optionally,this system may include a data compression logic circuit 56 forcompressing image data received from the logic circuit 46 before it isstored in the nonvolatile memory 57. The data compression logic circuit56 may be integral with the logic circuit 46.

Finally, whether configured as a vehicle intrusion detection system oras a compartment image data storage system, the vehicle interiormonitoring system preferably includes a supplemental source ofillumination 61 having a lens 62 as shown in FIG. 6A. A supplementalsource of illumination drive circuit 60 is connected to the supplementalsource of illumination 61. The drive circuit 60 also interfaces with andreceives control signals from the logic circuit 46 to drive thesupplemental source of illumination 61.

IV. Operation Of The Invention

FIG. 7 shows an overview of the logic flow chart and method forcontrolling the reflectance levels of any one or all of the mirrors ormirror segments 28a, 28b or 28c. It should be understood that thereflectance level of each of the mirrors 28a, 28b and 28c in theautomatic rearview mirror system of the present invention may becommonly or independently controlled. FIGS. 8A, 8B and 9 provide moredetail on the logic and method of FIG. 7.

In step S101 of FIG. 7, light information seen rearwardly of therearview mirror 1 is incident on the lens 30. In step S110, lightpassing through the lens 30 is refracted such that the light informationis imaged or focused onto the photosensitive surface of the photosensorarray 32. In step S120, the logic circuit 46 generates and outputs thearray control signals to the photosensor array 32. In step S130,photosensor element signals indicative of the light levels incident oneach of the photosensor elements 32a are generated. In step S140, thesephotosensor element signals are temporarily stored in RAM or any otherappropriate memory. In steps S150 and S160, the logic circuit 46determines values for the background light signal and the peak lightsignal for each zone corresponding to each of the mirrors 28. In stepS180, the logic circuit 46 uses the background and peak light signals ofstep S150 to determine the control signals required to cause each of themirrors 28 to achieve a desired reflectance level. Also, the logic andcontrol circuit 34 in step S180 reads and processes the states of theoptional sensitivity control circuit 42, force-to-day switch 36,force-to-night switch 40 and reverse-inhibit switch 38. In step S200,the mirror drive circuits 24 use the control signals determined in stepS180 to generate drive signals to cause the mirrors 28 to assume thedesired reflectance levels in step S210.

In one embodiment of the invention, the logic circuit 46 determines thebackground light signal B_(t) in steps S150 and S160 by calculating theaverage value of the photosensor element signals, previously stored inRAM in step S140, for the photosensor elements 32a in a lowest row orrows of the photosensor array 32 corresponding to an area below the rearwindow. With respect to FIGS. 3A and 3B, this means that the backgroundlight signal B_(t). is determined from photosensor element signalsgenerated by the photosensor elements 32a located in row D of thephotosensor matrix array 32. The logic circuit 46 may then output B_(t)to the RAM 50 for later processing. The logic circuit 46 may alsodetermine B_(t) by calculating an average value of all of thephotosensor element signals in the entire photosensor array 32. Moregenerally, the background light signal B_(t) for the rearward scene maybe determined by calculating the average value of X percent of thelowest photosensor element signal values in the RAM array RA(N,M), whereX is preferably 75, but typically may be in the range of 5 to 100.

Alternatively, an exposure period EP, as is described herein, may beused to determine the background light signal B_(t). An array responseAR may be determined using an array average method, as is also describedherein, for the photosensor element signal values corresponding to asub-array S(X) of the photosensor elements 32a of the photosensor array32 that correspond to an area below the rear window. The exposure periodEP may be varied within an operating point range OP±R, where OP is 10and R is 5 (8-bit data), but where OP may be from 5 to 175 and R may befrom 2 to 15. The exposure period is varied to maintain AR within OP +R.The background light signal B_(t) may therefore be determined whereB_(t) varies inversely with EP.

Additionally, the background light signal B_(t) is preferablychange-limited to determine a limited background light signal B_(Lt).The signal B_(t) may be change-limited, for example, by limiting changesin the background light signal B_(t) to 2% per time frame. A time framemay be, for example, 250 milliseconds or any other time relating to therate at which the logic circuit 46 samples the photosensor elementsignals from the photosensor array 32. The logic circuit 46 determinesthe change-limited value B_(Lt) used to determine the digital mirrorcontrol signal V_(DAC) (z) as follows: B_(Lt) =B_(L)(t-1) +C_(L) ×(B_(t)-B_(L)(t-1)), where B_(Lt) =the change-limited background light signalfor a current time frame t, B_(t) =the actual or substantially real-timebackground light signal for the current time frame t, B_(L)(t-1) =thechange-limited background light signal for a previous time frame (t-1)and C_(L) =the change-limit value. Additionally, the background lightsignal B_(t) from step S150 may be processed by the logic circuit 46 todetermine whether the change limited background light signal B_(Lt) isless than or greater than B_(L)(t-1). If B_(Lt) is greater thanB_(L)(t-1), then the logic circuit 46 may use a higher change-limitvalue C_(LH) to determine B_(Lt). If the background light signal B_(Lt)is less than or equal to B_(L)(t-1), then the logic circuit 46 may use alower change-limit value C_(LL) to determine B_(Lt). The values C_(LH)and C_(LL) are in the range of 0.01 to 2, but are preferably on theorder of about 0.02 or 2%.

The logic circuit 46 in step S150 also determines the peak light signalP(z) for each zone or sub-array S(X) of the photosensor matrix array 32.The peak light signal P(z) used to determine the appropriate mirrorcontrol signal V_(c) (z) for the mirror 28 may be determined by countingor summing the number of occurrences where the digital value for aphotosensor element signal is greater than a peak threshold value F foreach zone or sub-array S(X). For the preferred analog-to-digitalconverter having eight-bit data resolution, the logic circuit 46generates digital values indicative of light levels of light incident oneach photosensor element 32a in the range of 0 to 255 (2⁸ -1=255), withheadlights resulting in values in the range of about 200 to 255, so thatthe peak threshold value F is selected to be in the range of about 200to 255 but is preferably 245. The resulting count or sum P(z) provides ameasure of the peak light level for the following reasons.

One design objective of the lens 30 and the photosensor array 32combination is to be able to measure background light levels in theapproximate range of 0.01 to 0.1 lux when driving on sufficiently darkroads. This is achieved by ensuring that the lens 30, photosensorelements 32a and charge-to-voltage amplifiers 33c are able to measuresuch light levels and by providing a maximum exposure time. The maximumexposure time determines the operating frequency or sampling rate of thesystem 20. In the case of the described system, 1.5 MHz has been foundto be appropriate.

By varying the exposure time relative to a general background lightlevel B and using a substantially constant sampling rate, a wide rangeof background light levels in the range of 0.01 to 1000 lux can bemeasured. Thus, when the background light level is low, the exposuretime is relatively long such that headlights within the rearward areacause the affected photosensor elements 32a to saturate.Correspondingly, for higher background light levels, the exposure timeis reduced. Saturation occurs when the incident light charges thephotosensor element 32a to capacity so that any excess charge will leakor transfer to adjacent photosensor elements 32a. This charge leakageeffect is commonly referred to as "blooming." It has been found that acount of the number of photosensor elements 32a at or near saturation,i.e., those having digital values greater than the peak threshold valueF, provides an excellent approximation of the peak light levels and isfurther described in FIG. 8A. The above described method effectivelyextends the range of measurable light levels for the photosensor array32. As discussed, photosensor element signals are indicative of theincident light level or intensity and the time period for which they areexposed to such light. By operating the photosensor array 32 for a knownexposure time or exposure period EP, the incident light intensity may bedetermined from the photosensor element signal generated by eachphotosensor element 32a. After the exposure period, the logic andcontrol circuit 34 processes all of the photosensor element signals foreach photosensor element 32a of the photosensor array 32. This signalprocessing at least includes the process of storing the digital value ofeach photosensor element signal to obtain RA(N,M), but normally includesall other processing for each image data set RA(N,M) up to and includingthe generation of output control signals, such as the mirror controlsignal V_(c) (Z). The time from the beginning of the exposure period EPthrough the processing of each image data set RA(N,M) and the generationof the appropriate output control signals is referred to as theoperating or sampling period, and the frequency thereof is referred toas the operating frequency or sampling rate. The frequency at which theprocess is repeated may also be referred to as the frame rate or theimage sampling frequency. The rate of each sub-process (e.g., exposureperiod) within the sampling period is controlled by the system clock 47.Thus, the frame rate or image sampling frequency is essentially fixedfor a particular system clock frequency. The total period corresponds toa maximum exposure period EP and the total processing time relating toan image data set RA(N,M). The system clock frequency may be adjusted toscale the image sampling frequency, thereby adjusting EP. In summary,the maximum exposure period, the operating or sampling period, thesignal processing time and the frequency of the system clock 47 shouldbe considered in each application.

Alternatively, if an anti-blooming device is incorporated in thephotosensor array 32, such as is well known to those skilled in the art,then the peak light signal P(z) may be determined by calculating anaverage value of Y percent of the highest photosensor element signalvalues for each zone, where Y is preferably 10, but may be in the rangeof 1 to 25. When using this approach for determining P(z), it is alsopreferable to include logic to adjust the sampling rate or operatingfrequency of the logic circuit 46 to an appropriate value depending onB_(Lt).

The general background light signal B, whether B_(t) or B_(Lt), and thepeak light signal P(z) for each zone of the photosensor array 32, asdetermined in steps S150 and S160, are then used by the logic circuit 46to determine a mirror control signal V_(c) (z) as a function of theratio of B^(n) (n preferably has a value of one but may typically rangefrom 0.8 to 1.3) to P(z), i.e., V_(c) (z)=∫(B^(n) /P(z)). The controlsignal V_(c) (z) is then output to the mirror drive circuits 24 in stepS180 to drive the mirrors 28 or segments thereof to their desiredreflectance level in the steps S200 and S210.

FIG. 12 shows the logic flow chart and method for the vehicle interiormonitoring system or mode.

In step S301, the logic circuit 46 initializes the system, sets EP toits maximum and if used, SSI to a predetermined minimum, such as zero.Next in step S310, the logic circuit 46 reads any analog control inputsignals 70 (70a to 70n of FIG. 6A) and/or digital control input signals75 (75a to 75n of FIG. 6A) that may be used in the vehicle interiormonitoring mode.

In step S315, the photosensor element signals are generated, processedand stored in RAM 50 by the logic circuit 46 (see steps S101 to S140 ofFIG. 7). The logic circuit 46 also applies the lens correction factorLC(n,m) to each digital value Val RA(n,m) indicative of the photosensorelement signal L(n,m) of each photosensor element 32a in the RAM arrayRA(N,M) to correct for the effect of lens 30. This results in RA(N,M)containing the lens corrected digital value Val RA_(LC) (n,m) indicativeof the photosensor element signal of each photosensor element 32a.

Next, in step S320, the logic circuit 46 determines the array responseAR, which is indicative of either RA(N,M) (an entire image data frame orset RA.sub.(t) at time t) or of a selected sub-array or sub-set thereofRS(N_(S),M_(S)) (a partial image data frame or set RS.sub.(t) at timet), where N_(S) and M_(S) are the row and column dimensionscorresponding to a selected sub-array S(X) of the photosensor array 32.The logic circuit 46 processes the image data frame RA.sub.(t) using oneof the methods described below to determine the array response AR. Anappropriate operating point range OP±R is associated with each ARcalculation method.

The preferred method for determining AR is the array average method, inwhich the logic circuit 46 determines AR by averaging all of the datavalues Val RA_(LC) (n,m) in the image data frame RA.sub.(t) (or selectedsub-array RS.sub.(t)) where: ##EQU1## for n=1 to N, m=1 to M. Using thearray average method, it has been found that appropriate OP and R valuesare 127 and 20 (8-bit data resolution), respectively; however, theoperating point range may be non-symmetrical for some tasks by usingnon-symmetrical R values, such as +20 and -10.

An alternative method is the "no saturation" method, in which EP is setto its highest level at which there is no saturation or blooming in anyphotosensor element 32a. In this case, the logic circuit 46 reduces EPuntil the peak value of RA.sub.(t) or RS.sub.(t) is within the operatingpoint range OP±R. It has been found that appropriate OP and R values are249 and 5, respectively. Still another method involves maximizing theuseful image area, in which the logic circuit 46 determines AR bydetermining the difference between the number of photosensor elements32a having digital values of 0 and the number having digital values of255 (8-bit data resolution). In this case, appropriate OP and R valuesare 0 and 5% of the number of photosensor elements 32a corresponding tothe image data set RA.sub.(t) or sub-array RS.sub.(t). It should beunderstood that the specific values, such as 127 and 255, are based on8-bit data resolution and would be appropriately scaled for other dataresolutions.

In step S330 and S360, it is determined whether AR is in the operatingpoint range OP±R. If AR is outside the range, then the image data frameis either too bright (AR>OP+R) or too dim (AR<OP-R) and EP and SSI areincrementally increased or decreased according to steps S340, S341, S342or S350, S351, S352. This is repeated for every image data frameRA.sub.(t). The system thus optimizes EP and SSI for the particularcircumstances at system startup, and thereafter continues to adjust EPand SSI to maintain AR within the operating point range OP±R as lightingconditions change.

If AR is within the operating point range OP±R, then the vehicleinterior monitoring system/mode enters a primary task routine or mode instep S370, such as the vehicle intrusion detection system/mode (S400) ofFIG. 12A or the compartment image data storage system/mode (S500) ofFIG. 12B. After completing the primary task routine, the program returnsto the vehicle interior monitoring mode to generate and store anotherimage data frame RA.sub.(t).

V. The Preferred Embodiments

The general lighting conditions of the rearward scene can be defined asfollows: the background light level of the viewed rearward scene is Band the peak light level for each zone or sub-array S(X) is P(z). Acontrast ratio C(z) may be defined as the ratio of the peak light levelP(z) for each zone to the general background light level B; thus,C(z)=P(z)/B. Given the background light level B, the human eye cantolerate varying peak light levels in the viewed rearward scene up to aparticular contrast ratio tolerance C_(T). Contrast ratios greater thanC_(T) initially cause discomfort and are generally known as glare. Asthe eye adjusts its light sensitivity to protect itself from thediscomforting peak or glare light levels, vision is reduced and theglare may become disabling. Thus, the maximum tolerable peak light levelP_(T) of the viewed rearward scene is equal to the product of thecontrast ratio tolerance C_(T) and the background light level B, i.e.,P_(T) =C_(T) ×B.

The desired reflectance R_(d) (z) of a variable reflectance mirror foreach zone is that reflectance level which reduces a peak light levelP(z) to a value equal to the maximum tolerable peak light level P_(T),i.e., P_(T) =R_(d) (z)×P(z) or R_(d) (z)=P_(T) /P(z), and substitutingthe expression for P_(T), R_(d) (z)=(C_(T) ×B)/P(z). However, themaximum tolerable contrast ratio C_(T) varies across the population dueto aging and other factors; accordingly, a sensitivity factor S may beused to account for this variation in contrast tolerance sensitivity sothat R_(d) (z)=(S×C_(T) ×B)/P(z). Selecting the desired reflectanceR_(d) (z) for each zone provides maximum information from the rearwardscene viewed in each mirror or mirror segment while reducingdiscomforting or disabling peak light levels to tolerable levels.

The mirror control signal V_(c) (z) required to obtain the desiredreflectance R_(d) (z) depends on the particular variable reflectancemirror element that is used. For electrochromic mirrors, avoltage-reflectance relationship can be approximated and generallydefined. In general, an electrochromic mirror has a reflectance level Rhaving a maximum value of R₁ with an applied voltage V_(app) of 0 volts.As the applied voltage V_(app) is increased, the reflectance level Rperceptually remains on the order of R₁ until V_(app) reaches a value ofapproximately V₁. As V_(app) is further increased, the reflectance levelR decreases approximately linearly until a minimum reflectance ofapproximately R₂ is reached at a voltage V₂. Thus, the applied voltageV_(app) can be approximately defined as:

ti V_(app) =V₁ +(R₁ -R)×(V₂ -V₁)/(R₁ -R₂)

Substituting desired reflectance R_(d) (z) for the reflectance R resultsin the mirror control signal, the voltage of which is determined asfollows:

    V.sub.c (z)=V.sub.1 +(R.sub.1 -S×C.sub.T ×B/P(z))×(V.sub.2 -V.sub.1)/(R.sub.1 -R.sub.2).

To obtain a digital value V_(DAC) (z), V_(C) (z) is scaled by a factorthat is the ratio of the maximum digital value to the value V₂ ; thus,for eight-bit data resolution V_(DAC) (z)=255 V_(c) (z)/V₂, andsubstituting for V_(c) (Z):

    V.sub.DAC (Z)=255(V.sub.1 +(R.sub.1 S×C.sub.T ×B/P(z))×(V.sub.2 -V.sub.1)/(R.sub.1 -R.sub.2))/V.sub.2.

FIG. 8A provides further detail on the steps S150 and S160 where thelogic circuit 46 determines the background and peak light signals. Moreparticularly, steps S151, S152, S159 and S160 provide two processingloops for sequentially determining the digital values indicative of thephotosensor element signals, Val RA(n,m), in the RAM array RA(N,M) foreach of the photosensor elements 32a of the photosensor array PA(N,M).

In step S153, a lens correction factor LC(n,m) is applied to eachdigital value indicative of the photosensor element signal, Val RA(n,m),to correct for the effects of lens 30, which results in a lens correcteddigital value of the photosensor element signal Val RA_(LC) (n,m). Theseeffects are typically referred to as cosine effects or Lambert's Laweffects. The lens correction factor LC(n,m) depends on the radialdistance of the photosensor element 32a from a central axis of the lens30, and is typically in the range of 1 to 15 but will depend on thegeometry of the lens and the selected photosensor array. The lenscorrection factor LC(n,m) applied to each Val RA(n,m) may be calculatedaccording to Lambert's Law each time Val RA(n,m) is processed. Morepreferably, the logic circuit 46 initially stores an array of valuesLC(n,m) in the RAM 50 for each photosensor element 32a of thephotosensor array PA(n,m) during an initialization routine.Alternatively, the size of the photosensor elements 32a of thephotosensor array 32 may be adjusted to correct for the lens effects ateach photosensor element 32a.

As discussed, it has been found that light levels for headlightsgenerally result in an eight-bit digital value greater than a peakthreshold value F having a value of about 245. Correspondingly, duringnon-daylight operation of the automatic rearview mirror system 20,background light levels generally result in eight-bit digital valuesindicative of the light levels incident on the photosensor elements 32athat are less than or equal to the peak threshold value F.

Accordingly, the lens corrected value Val RA_(LC) (n,m) is compared instep S154 to the peak threshold value F. If Val RA_(LC) (n,m) is lessthan or equal to F it is used to increment a counter B_(count), in thelogic circuit 46, by 1 in step S157 (thereby indicating that a valueless than or equal to F has been identified) and by increasing a valueB_(Sum), by the value of Val RA_(LC) (n,m) in step S158, where B_(Sum)is the sum of all the values of Val RA_(LC) (n,m) which are less than orequal to F. The background light signal B_(t) is then determined in stepS161 as follows: B_(t) =B_(Sum) /B_(Count). If Val RA_(LC) (n,m) isgreater than F in step S154, then the logic circuit 46 uses a counterP(z) indicative of the peak light levels for each of the zones orsub-arrays S(X) of the photosensor array PA(N,M), which is incrementedby 1 as previously described. More particularly, Val RA_(LC) (n,m) istested in step S155 to determine whether it originates from a particularzone or sub-array S(X), where X=1 to Z. If Val RA_(LC) (n,m) does notfall within a defined zone or sub-array S(X), then P(z) is notincremented; otherwise, P(z) is incremented in step S156 for theappropriate zone.

If the photosensor array 32 is arranged to view the rearward areathrough the active layer of the variable reflectance element 1a, then acolor correction factor CC is applied in step S162 to B_(t) and P(z) tocompensate for any reduction in transmittance when the reflectance level(and transmittance) of the rearview mirror 1 is reduced. The value of CCis determined from the last calculated value indicative of the digitalmirror control signal V_(DAC) (z) applied to the rearview mirror 1. Instep S163, a change-limited background light signal B_(Lt) is determinedas has been described previously.

FIG. 8B provides further detail on step S180 where the logic circuit 46determines the appropriate digital mirror control signal V_(DAC) (z) foreach zone or sub-array S(X) and corresponding mirror 28. In steps S181and S182, V_(DAC) (z) is calculated for each mirror 28. In step S183,the logic circuit 46 reads a state IN1 of the reverse-inhibit switch 38and if the vehicle is in reverse gear so that IN1 is high, then alldigital mirror control signals V_(DAC) (z) are set to 0 in step S184forcing the mirror 28 to its maximum reflectance level. In step S185, astate IN2 of the force-to-day switch 36 is read and if IN2 is high, thenall digital mirror control signals V_(DAC) (z) are set to 0 in step 186forcing the mirror 28 to its maximum reflectance level. Finally, in stepS187, a state IN3 of the force-to-night switch 40 is read and if IN3 ishigh, then all digital mirror control signals V_(DAC) (z) are set to 255(the maximum digital value for eight-bit data resolution) in step S188forcing the mirror 28 to its minimum reflectance level.

FIG. 9 shows another view of the logic flow whereby the rearview mirror,the left side view mirror and the right side view mirror (oralternatively three mirror segments) are independently driven to theirdesired reflectance levels by the independent and separate control anddrive signals using photosensor element signals from three photosensorelement sets (i.e., the sub-arrays S(1), S(2) and S(3) of photosensorelements 32a in the photosensor array PA(n,m)). The specific subroutinesshown in FIGS. 8A and 8B corresponding to the general steps shown inFIG. 7 are also used with the general steps shown in FIG. 9.

In step S201, light incident on the lens 30 is focused in step S210 ontothe photosensor array 32 comprising the first, second and third sets ofphotosensor elements 32a in zones a, b and c, respectively. Next, instep S211, the light incident on the first photosensor element set inzone a generates a first set of photosensor element signals, which, instep S211', are then stored in RAM and later used by the logic circuit46 to determine a first peak light signal in step S212.

In step S221, the light incident on the second photosensor element setin zone b generates a second set of photosensor element signals, whilein step S231, the light incident on the third photosensor element set inzone c generates a third set of photosensor element signals. The secondset of photosensor element signals, generated in step S221 are alsostored in step 221' in RAM and then used by the logic circuit 46 todetermine a second peak light signal in step S222. Similarly, the thirdset of photosensor element signals, generated in step S231, is nextstored in step S231' in RAM and then used by the logic circuit 46 todetermine a third peak light signal in step S232.

In step S213, photosensor element signals generated from selectedphotosensor elements on which light is incident in step S210 are used todetermine the background light signal.

In step S214, the logic circuit 46 uses the background light signaldetermined in step S213 and the first peak light signal determined instep S212 to determine a first control signal. Similarly, the logiccircuit 46 uses the background light signal of step S213 and the secondpeak light signal determined in step S222 to determine a second controlsignal in step S224. In the same manner, the background light signal ofstep S213 and the third peak light signal of step S232 are used by thelogic circuit 46 to determine a third control signal in step S234.

The first control signal determined in step S214 is used by the drivecircuit 24a to generate a first drive signal in step S215. This firstdrive signal drives the rearview mirror 28a to a desired reflectancelevel in step S216. Likewise, the second control signal determined bythe logic circuit 46 in step S224 is used by the drive circuit 24b togenerate a second drive signal in step S225, which is then used to drivethe left side view mirror 28b to a desired reflectance level in stepS226. Finally, the third control signal determined by the logic circuit46 in step S234 is used by the drive circuit 24c to generate a thirddrive signal to drive the right side view mirror 28c to a desiredreflectance level in step S236. Of course, the first, second and thirdcontrol signals may also be used to control the segments of a mirror 28.

Finally, as previously discussed, one advantage of the present inventionis that it is able to use a single photosensor array 32 to determineboth a background light level and a peak light level for controlling thereflectance level of a mirror. This is especially advantageous where thesensor must be placed outside the interior of the vehicle to view therearward scene. This may be required, for example, in certain truck typevehicles where only exterior side view mirrors may be used and automaticoperation is desired. Accordingly, the photosensor array 32 may belocated with each side view mirror. The other electronics for theautomatic rearview mirror system 20, described previously, may belocated either with the photosensor array 32 in each side view mirror,inside the vehicle cab or elsewhere in or on the vehicle. A desiredreflectance level for each exterior side view mirror may then beaccurately determined using both the determined background light leveland peak light level using only a single photosensor array 32 for eachmirror.

FIGS. 12 and 12A show the logic flow charts of the vehicle interiormonitoring system configured as a vehicle intrusion detection system(primary task S400).

In step S401, the current image data frame RA.sub.(t) is processed toenhance its contrast characteristics so that it is largely unaffected bychanging light levels or shadows, etc. Preferably, the logic circuit 46selects an appropriate sub-array RS.sub.(t) corresponding to thesub-array S(X) (or other appropriate set) of photosensor elements 32a ofthe photosensor array 32 containing the relevant image information.

As discussed, the particular area of interest or significance in thephotosensor array 32 may be a sub-array S(X) of photosensor elements 32aof the photosensor array 32 (or other appropriate set not necessarilyrectangular in shape, such as a trapezoid). The ability to select imagedata corresponding to S(X) is important because some sets of photosensorelements 32a may provide image information that is redundant, irrelevantor even damaging to a particular application and should therefore beignored by the logic circuit 46. A significant advantage of thephotosensor array 32 over other sensing technologies is its ability toprovide selected image information so that the logic circuit 46 needonly process RS.sub.(t) when, for example, the relevant sub-array S(X)and corresponding sub-array RS.sub.(t) contain all the image informationnecessary to a particular application. For example, in the automaticrearview mirror and vehicle intrusion detection system described herein,a selected sub-array S(X) of photosensor elements 32a may provide imageinformation as shown in FIGS. 3A and 3B, which may be used by logiccircuit 46 to provide information regarding the location and intensityof the headlights of following vehicles. To the extent that other areasof the photosensor array 32 do not provide such image information, theymay be ignored. Likewise, since the same photosensor array 32 may beused for vehicle intrusion detection, the logic circuit 46 need onlyprocess the image information of FIG. 2A that excludes the imageinformation of FIGS. 3A and 3B. Without this ability to selectparticular sets or sub-arrays, at least more intensive processing may berequired to distinguish between unauthorized activity within the vehicleand irrelevant activity outside the vehicle.

After selecting the appropriate set of image data, the logic circuit 46processes the values in RA.sub.(t) to enhance the contrast or robustnessof that image data frame. Excluding photosensor elements 32a in theoutside rows and columns of the photosensor array 32, every photosensorelement E(n,m) has eight (8) adjacent photosensor elements 32a orneighbors: E(n-1,m); E(n,m-1); E(n-1,m-1); E(n+1,m); E(n,m+1);E(n+1,m-1); E(n-1,m+1); and E(n+1,m+1). Therefore, a contour valueCV(n,m) for each photosensor element E(n,m) may be calculated bydetermining the average of the differences between the value Val RA_(LC)(n,m) of the photosensor element E(n,m) and the value of each neighbor.If the photosensor element value is an n-bit value, then CV(n,m) is alsoan n-bit value. Thus, using 8-bit data resolution, for example, ifE(n,m) has a 0 value and each neighbor has a value of 255, then CV(n,m)is 255. If E(n,m) has a value of 255 and each neighbor has a 0 value,then CV(n,m) is 255. Both examples indicate a high degree of localcontrast or discontinuity. On the other hand, if E(n,m) and eachneighbor has a value of 127, then CV(n,m) is 0, which indicates a lowdegree of local contrast. Thus, the logic circuit 46 uses the abovemethod, to determine the contrast value CV(n,m) for each value ValRA_(LC) (n,m) of RA.sub.(t) to obtain a contour enhanced image dataframe RC.sub.(t) in which the "harder" image contours or discontinuitiesare emphasized or enhanced, while "softer" image contours are reduced insignificance.

Next, in step S402, the logic circuit 46 correlates the current imagedata frame RC.sub.(t) and a reference image data frame RC_(REF)(t-1) bycomparing them to determine an image correlation factor IC. This factoris indicative of the correlation or degree of similarity (or difference)between the two image data frames independent of the particular image orphotosensor array size. An IC value of 0 indicates no image similarityand an IC value of 1 indicates a perfect match. In particular, the imagecorrelation factor IC is indicative of the number of correspondingphotosensor elements 32a within the photosensor array 32 (or sub-arrayS(X)) having the same value Val RA_(LC) (n,m) within some tolerancevalue T for the current and reference image data frames or sets. Thetolerance value T accounts for minor image variations, such as may becaused by system vibration or other system "noise". Thus, the value fromthe current image data frame RC.sub.(t) corresponding to photosensorelement E(1,1) is compared with the value from the reference image dataframe RC_(REF)(t-1) corresponding to photosensor element E(1,1), and if:

    Val RC.sub.(t) (1,1)=Val RC.sub.REF(t-1) (1,1)±T,

then the RC.sub.(t) and RC_(REF)(t-1) values of photosensor elementE(1,1) correlate. This is done for all photosensor elements 32a withinthe photosensor array 32 or selected sub-set thereof, and the logiccircuit 46 stores and sums each correlation occurrence for each elementE(n,m). The logic circuit 46 then divides the resulting sum ofcorrelation occurrences by the number of elements E(n,m) considered indetermining the image correlation factor IC.

Next, in step S403, the logic circuit 46 determines whether certainsystem start-up criteria are met. This is done to ensure that a stableimage data frame RC.sub.(t) is stored as RC_(REF)(t). Importantly,RC_(REF)(t) must correspond to an optimized and stable image data frameRC.sub.(t). When power is initially supplied to light sensing and logiccircuit 26, electrical and thermal transients occur as is typical forsilicon integrated circuits. For the system described herein,satisfactory start-up criteria include: (1) a minimum number of imagedata frames that must be processed to allow electrical stabilization andthe completion of the majority of EP and SSI optimization, where theminimum number of data frames is preferably 25 but may be in the rangeof 15 to 40; and (2) a stable reference image RC_(REF)(t), whereRC_(REF)(t) is sufficiently stable when AR is within the operating pointrange OP±R and IC exceeds 0.95 for at least 2 to 10 image data frames,but preferably 4 image data frames.

If the start-up criteria are not met in step S403, then, in step S404,the logic circuit 46 stores RC.sub.(t) in RAM 50 as a reference imagedata frame RC_(REF)(t) (which is RC_(REF)(t-1) where the current imagedata frame is RC.sub.(t) on the next system cycle) and the programreturns to step S310. If the start-up criteria in step S403 are met,then the program goes to step S405.

In steps S405 and S406, threshold values T₁ and T₂ are used to determinethe degree to which the current and reference image data frames match ormismatch. The values of T₁ and T₂ depend on the particular applicationand the degree of confidence or reliability required in thematch/mismatch conditions of steps S405 and S406. For the vehicleintrusion detection system, it has been found that appropriate thresholdvalues may range from 0.0 to 0.6 for T₁ and from 0.95 to 1.0 for T₂, butare preferably 0.6 and 0.95 for T₁ and T₂, respectively. Due to image orsystem variations, perfect image correlation does not normally occur;therefore, compared image data frames having an IC value greater than0.95 are considered a match, those having an IC value less than 0.6 areconsidered a mismatch and those having an IC between T₁ and T₂ areneither a definite match nor a definite mismatch.

More particularly, if IC exceeds T₁ in step S405, then the logic circuit46 determines whether IC exceeds T₂ in step S406. If IC does not exceedT₂, then the program returns to step S310 since there is neither a matchnor a mismatch condition. If IC does exceed T₂, then there is a matchand the logic circuit 46 updates the reference image data frameRC_(REF)(t). It should be understood that RC_(REF)(t) may be the same asRC.sub.(t) or may represent any appropriate combination of two or moreimage data frames. For example, RC_(RFF)(t) may be determined using adigital lag filter:

    RC.sub.REF(t) =RC.sub.REF(t-1) +K×(RC.sub.(t) -RC.sub.REF(t-1)),

where K may be a constant. After the logic circuit 46 updatesRC_(REF)(t) and stores it in the RAM 50, the program again returns tostep S310.

If IC does not exceed T₁ in step S405, then the image data frames areconsidered a mismatch. Even though T₁ is selected so that onlysignificant differences between RC.sub.(t) and RC_(REF)(t-1) provide amismatch condition, the logic circuit 46 determines in step S408 whetherthe mismatch condition is a valid intrusion condition. This is becausethere are conditions that result in the logic circuit 46 erroneouslydetermining a mismatch condition. For example, automotive electricalsystem noise may affect the ability of the photosensor array 32 toprovide accurate photosensor element signals, although this normallyoccurs only for short periods given the nature of such noise. While notall system applications may require the same level of confidence for acorrect mismatch condition, it has been found that requiring a number ofsuccessive mismatch conditions represents a good validation test forstep S408. In particular, it has been found that this validation testbetter ensures that the mismatch condition is valid by requiring from 2to 300 successive mismatch conditions. Alternatively, the validationtest may require from 2 to 300 initial mismatch conditions and allow anumber of match conditions in step S405, where the number of matchconditions may be from 1 to 15 depending on the required number ofmismatch conditions.

If the logic circuit 46 determines that the mismatch condition is notvalid in steps 408, then the program will go to step S310. If themismatch condition is valid, then the logic circuit 46 outputs one ormore control signals in step S409. The control output signals aregenerally of two types: (1) signals that may be used to control directlycertain vehicle hardware (lights, horn, etc.); and (2) signals that maybe used as inputs to other vehicle controller systems that directlyinterface with such hardware. The logic circuit 46 may output anycombination of these control output signals depending on the desiredlevel of integration between the system of the present invention andother vehicle systems. Digital control signals, such as bistable signalsor digitally coded words interpreted by other vehicle systems, aretypical for most applications. If the logic circuit 46 outputs bi-stablecontrol signals directly to vehicle hardware, then the control outputsignal lines may be latched in a high or low state to control thevehicle hardware. If the logic circuit 46 outputs control signals to avehicle controller system, then a higher protocol level, (such asdigitally coded words) may have to be output from the logic circuit 46.

FIG. 12B shows the logic flow chart of the compartment image datastorage system configuration (primary task routine S500) of the vehicleinterior monitoring systems of FIG. 12.

In step S501, the image data frame RA.sub.(t) (although this may beRC.sub.(t)) is tested to determine whether it is valid. To determinewhether RA.sub.(t) is valid in step S501, the logic circuit 46 maydetermine whether the array response AR is within the operating pointrange OP±R. More stringent validity tests may include vehicle featurerecognition, in which the system attempts to identify reference vehiclefeatures, such as the seats or window pillars, and if the logic circuit46 cannot identify these reference features in RA.sub.(t), then itdetermines that RA.sub.(t) is invalid. If RA.sub.(t) is valid, thenRA.sub.(t) may be optionally compressed in step S502 using anyappropriate digital compression method to reduce the amount of imagedata. Next, in step S503, the logic circuit 46 stores the image data inthe nonvolatile memory 57 on a first-in-first-out (FIFO) basis. As willbe described further below, the program may end or return to step S310to obtain and process additional image data frames depending on theparticular application. If RA.sub.(t) is not valid, then in steps S504,505, S506 and S507, the logic circuit 46 determines whether thephotosensor 2 has been intentionally defeated so that an accurate imagedata frame of the vehicle interior or compartment cannot be generatedand stored in the nonvolatile memory 57.

More particularly, in steps S504 and S506, if it is determined that bothEP and SSI are minimums, then the photosensor 2 is probably beingdefeated by an intruder or vehicle thief who is blinding the photosensor2 by directing a light source, such as a bright flashlight, directly atthe photosensor 2. This action saturates the photosensor array 32 sothat the image data frame appears "white". Since the photosensor array32 normally does not saturate when both EP and SSI are at theirminimums, a "white" image data frame would not normally occur. In stepsS505 and S507, if it is determined that both EP and SSI are maximums,then the photosensor 2 is probably being defeated by an intruder who isblinding the photosensor by placing a piece of tape or other opaquematerial over the lens 30 (or window) which the photosensor array 32uses for "seeing" the vehicle interior 100. This action results in a"black" image data frame. Since SSI is maximized to allow thephotosensor array 32 to generate images even if there is insufficientnatural light, a "black" image data frame would also not normally occur.

If steps S504, S505 and S507 result in a "black" image condition orsteps S504 and S505 result in a "white" image condition, then the logiccircuit 46 outputs a control signal in step S508 to the vehiclecontroller to disable the ignition control device and/or to the vehiclecontroller system to activate the horn and lights. Otherwise, EP and SSIhave not reached their adjustment limits, and the system attempts tooptimize them and generates another image data frame which is then againtested to determine its validity in step S501.

VI. Integrated Headlight Control System

It is generally important for driver safety reasons that the headlightsand sidelights of operating vehicles are turned on as night approachesor when background lighting levels fall below approximately 500 lux.More particularly, it is desirable to have the vehicle's headlights andsidelights automatically turn on when background lighting levels fall toa sufficiently low level and automatically turn off when backgroundlighting levels rise sufficiently.

While there are other automatic headlight control systems, such systemsrequire that the photocells, which are used to control the headlights,be located and positioned so that they generally face upward either toavoid the effects of oncoming headlights for generally forward facingphotocells or to avoid the effects of following headlights for generallyrearward facing photocells.

An advantage of the automatic rearview mirror system 20 is that thebackground light signal B_(Lt) may be used to automatically turn on andoff a vehicle's headlights and sidelights by controlling the vehiclelighting switch 45. Importantly, since BLt is determined regardless ofthe presence of peak light sources, such as oncoming or followingheadlights, the directional constraints on how and where the sensor islocated or positioned are avoided. Accordingly, using the photosensorarray 32 of the present invention to provide additional vehicle lightingcontrol functions results in lower costs and improved reliability overother headlight control systems.

The limited background light signal B_(Lt) has been described for thepurpose of controlling the reflectance levels of an automatic rearviewmirror system 20. Additionally, the logic circuit 46 may use B_(Lt) togenerate a vehicle lighting control signal to control the vehiclelighting switch 45 to turn on and off automatically the vehicle'sheadlights and sidelights. The ability to use B_(Lt) is importantbecause the vehicle lighting switch 45 should not be responsive to rapidor small fluctuations in background light levels in the region of thedesired point at which the vehicle lighting switch is turned on or off,i.e., the switch point. Such fluctuations can be caused by the shadowingeffect of overhanging trees or structures or the lighting differencesbetween the eastern and western skylines at dawn and dusk which may beencountered when turning the vehicle.

Additionally, hysteresis is also provided between the switch-on andswitch-off conditions of the vehicle lighting switch 45 to furtherstabilize operation of the switch 45 in such fluctuating lightconditions. More specifically, if the required switch point for fallinglight The levels is SP, then the switch point for rising light levels isSP×(1+H), where H is a hysteresis factor typically in the range of about0.005 to 0.5, but is preferably 0.2. Thus, if B_(Lt) is less than SP,then the vehicle lighting control signal to the vehicle lighting switch45 is set high to turn on the vehicle's headlights and sidelights. IfB_(Lt) is greater than SP×(1+H), then the vehicle lighting controlsignal to the vehicle lighting switch 45 is set low to turn off thevehicle's headlights and sidelights.

Additionally, if the photosensor array 32 and logic circuit 46 are bothpowered directly by the vehicle's electrical system through the ignitionswitch, then a time delay td may be provided such that if the ignitionswitch is turned off when the headlight control signal is set high, thevehicle lighting control signal will remain high for a time t_(d) andthereafter fall to a low value to turn off the vehicle's headlights andsidelights. A manual control may also be provided to allow the driver toadjust the time delay t_(d).

The vehicle lighting control signal and, more specifically, the lightingcontrol switch 45 may also be used to inhibit automatic control of theautomatic rearview mirror system 20. For example, if the vehiclelighting control signal indicates that the vehicle lighting should beturned off, then the logic and control circuit 34 may be used to enablesensitivity switch 42 or some other switch allowing the driver tomanually adjust the reflectance level of the mirrors 28. Thus, thedriver may manually select a lower reflectance level during daylightconditions to provide protection against peak light sources, such as abright setting sun. As background light levels fall or duringnon-daylight conditions, the vehicle lighting control signal wouldindicate non-daylight conditions and the logic and control circuit 34may then be used to disable manual control and return the automaticrearview mirror system 20 to full automatic control.

FIG. 6B shows another embodiment of a stand-alone vehicle lightingcontrol system, which has a number of the components identified withrespect to FIG. 6. The vehicle lighting control system of FIG. 6B mayalso be integrated with automatic rearview mirror system and vehicleinterior monitoring system described herein. In FIG. 6B, however, thephotosensor array 32 is directed generally forward of the vehicle sothat it may sense a field of view forward of the rearview mirror 1. Theforward field of view is through the vehicle's front windshield andgenerally in line with the primary vehicle direction. In the embodimentof the vehicle lighting control system as described herein, thephotosensor array 32 comprises a plurality of photosensor elements 32aarranged in 160 columns and 120 rows (a 160×120 array) and has a forwardfield of view of approximately 50 degrees centered at the vehicle centerline and a vertical field of view of approximately 30 degrees, where thevertical field of view is approximately 10 degrees above and 20 degreesbelow the horizon in the forward field of view. It should be understoodthat the forward field of view may also be provided to the photosensorarray 32 by using any appropriate image directing optics or otherappropriate means for directing a forward field of view onto thephotosensor array 32 regardless of its orientation.

The logic and control circuit 34 processes the photosensor array signalscorresponding to the forward field of view to determine an appropriatevehicle lighting configuration depending on the light information in theforward field of view. The methods used by the logic and control circuit34 to determine the appropriate vehicle lighting configuration aredescribed below. After determining the appropriate vehicle lightingconfiguration, the logic and control circuit 34 generates and appliescontrol signals to headlight switches 29, which comprise a low beam modeswitch 29a, a mid beam mode switch 29b and a high beam mode switch 29c,and to a vehicle running lights switch 31 and tail lights and sidelights switches 35. Also shown in FIG. 6B is a sensitivity controlcircuit 41, which may be used to control the level of hysteresis in thevehicle lighting control system, and manual vehicle light switches 43for manually controlling the vehicle lights.

The photosensor array 32 is preferably located within the vehicleinterior since this provides protection against the outside elements,including dirt, moisture, rain and snow, as well as reduced exposure toultraviolet light, and generally provides a relatively controlledenvironment, including temperature environment. It should be understood,however, that the photosensor array 32 may also be located in one orboth of the external sideview mirrors 4 and 5, or in any otherappropriate location on the vehicle.

The methods defined for determining the change-limited background lightsignal B_(Lt) may also be used to determine a change-limited backgroundforward light signal B_(LFt) that may be used to control the vehiclelighting system. Also, the methods previously described for determiningand identifying peak light levels may generally be used to determine andidentify whether there are other headlights and taillights in thedriver's forward field of view. The logic and control circuit 34 usesthis information to control automatically the vehicle headlights (lowbeam, mid beam and high beam modes) so as to limit the annoyance ordebilitation of other vehicle drivers forward of the vehicle. The methodfor processing the forward field of view image is the same as that shownthrough step S140 in the flow chart of FIG. 7A, and is generally thesame as to steps S150 and S160 as detailed in the flow chart FIG. 8A,except that steps S155, S156 and S162 are excluded. FIGS. 13A, 13B, 13Cand 13D are the flow charts that show the methods used by the logic andcontrol circuit 34 to determine the appropriate vehicle lightingconfiguration and to control the vehicle lighting system. The methodsdetailed in FIGS. 13A, 13B, 13C and 13D may generally be described asfollows:

After the logic and control circuit 34 determines B_(LFt), it determineswhether B_(LFt) exceeds a threshold B_(DD), which corresponds to thelight level at dawn, dusk or a comparable lighting condition. If B_(LFt)exceeds B_(DD), then a flag F_(DAY) corresponding to a daytimecondition, which indicates that the vehicle running lights, if any, maybe turned on but that vehicle headlights and taillights should otherwisebe off, and resets to zero flags F_(FLOW), F_(MID) and F_(HIGH), whichrespectively correspond to the low, mid and high beam modes for thevehicle headlights. If B_(LFt) is less than B_(DD) and exceeds athreshold B_(N), which corresponds to a light level at night below whichthe mid or high beam modes may be operated, then the logic and controlcircuit 34 sets F_(LOW) to 1 and resets F_(DAY), F_(MID) and F_(HIGH).

If B_(LFt) is less than B_(N), then the logic and control circuit 34processes a mid zone, which corresponds to a Sub-Array S(X) within theArray PA(N,M) of the photosensor array 32. This mid zone or zone ofinterest represents an appropriate area of the forward field of viewimage, in which the vehicle headlights may be set to their mid beam modeif there are no other vehicles as indicated by other vehicle lightsources (headlights or taillights) within the mid zone. If there are noother vehicle light sources, then the logic and control circuit 34 setsF_(MID) to 1 and resets F_(LOW). Otherwise, F_(LOW) remains set, and thelogic and control circuit 34 determines and processes the next set ofphotosensor element signals.

If, however, F_(MID) is set to 1, then the logic and control circuit 34processes a high zone corresponding to the Array PA(N,M). The high zonerepresents an appropriate area of the forward field of view image, inwhich the vehicle headlights may be set to their high beam mode if thereare no other vehicle light sources within the high zone. If there are noother vehicle light sources, then the logic and control circuit 34 setsF_(HIGH) to 1 and resets F_(MID). Otherwise, F_(MID) remains set, andthe system determines and processes the next set of photosensor elementsignals.

More complex vehicle lighting configurations may be controlled bydetermining an appropriate zone of interest for each available vehiclelighting mode or pattern.

Also, as discussed above with respect to the first embodiment of avehicle lighting control system, hysteresis is used to moderate thefrequency of transitions between the various beam modes and is reflectedin FIGS. 13A, 13B, 13C and 13D by low beam counter LC, mid beam counterMC, high beam counter HC and night counter NC, each having correspondinghysteresis values LC1, MC1, HC1 and NC1, respectively. The hysteresisvalues may correspond to about 1 to 30 forward field of view imageframes, and therefore correspond to a certain period of time since eachimage frame takes on the order of about 0.1 seconds to process. Itshould also be understood that in the described embodiment, hysteresishas only been provided for transitions from low to mid or mid to hightransitions, while transitions from high to mid or mid to low occurafter the processing of only one image frame. Of course, hysteresis mayalso be used for transitions from high to mid or mid to low. Also,transitions to the initial low beam mode may be delayed on the order of15 seconds to five minutes, rather than occurring within one image frameas described herein. Further, in addition to or alternatively tohysteresis, specific time delays of from about 1 to 15 seconds, or anyother appropriate delay be used for transitions between beam modes.

Also, the vehicle driver may use the sensitivity control circuit 41 toadjust the level of hysteresis. The vehicle driver may also use themanual vehicle light switches 43 to override the vehicle lightingcontrol system.

As discussed, FIG. 13A shows the initialization of the system and theinitial low beam mode determination, FIG. 13B shows the initial mid andhigh beam mode determinations, FIG. 13C shows subsequent transitionsfrom the mid beam mode to either the low or high beam modes, and FIG.13D shows subsequent transitions from the high beam mode to the mid andlow beam modes.

As to FIG. 13A, in the initialization step S600, the logic and controlcircuit 34 sets flag F_(Day) to 1, sets flags F_(LOW), F_(MID), F_(HIGH)and F_(N) to 0, and sets counters LC, MC, HC and NC to 0.

Next, in step S610, the logic and control circuit 34 determines B_(LPt)as previously described. In step S620, if B_(LFt) is not less thanB_(DD), then the logic and control circuit 34 determines whether LCequals or exceeds LC1 in step S621. If LC is less than LC1, then LC isincremented in step S624 and the processing is returned to step S610. IfLC equals or exceeds LC1, then the logic and control circuit 34 in stepS622 sets F_(Day) to 1, resets flags F_(LOW), F_(MID) and F_(HIGH) to 0and also resets a flag F_(TSL), which corresponds to the status of thevehicle tail lights and side lights. Next, in step S623, the logic andcontrol circuit outputs control signals to disable all vehicle nightlights, including the headlights, side lights and tail lights.

If in step S620, B_(LFt) is less than B_(DD), then the system goes tostep S630. In step S630, if LC exceeds 0, then LC is decremented in stepS631 and the system returns to step S610. If LC equals 0 in step S630,then the logic and control circuit 34 sets F_(Day) to 0 in step S640,and then goes to step S650. In step S650, if B_(LFt) is not less thanB_(N), then the logic and control circuit 34 determines whether NCequals or exceeds NC1 in step S651. If not, then NC is incremented instep S653. If yes, then NC is set to NC1 in step S652. In either case,F_(N) is then reset and the system goes to step S900. If B_(LFt) is lessthan B_(N), the system goes to step S660. If NC exceeds 0 in step S660,then NC is decremented in step S661 and F_(N) is reset in step S662,after which the system goes to step S900. If NC equals 0 in step S660,then F_(N) is set to 1 in step S670. Next, in steps S700 and S800, ifF_(MID) and F_(HIGH) are not 1, then the system also goes to step S900.In step S900, F_(LOW) and F_(TSL) are set and LC is set to LC1. Next, instep S910, the logic and control circuit 34 enables the tail and sidelights (TSL) and low beam mode, and proceeds to step S920.

Next, FIG. 13B shows the logic for making an initial transition from thelow beam mode to the mid beam mode and for making an initial transitionfrom the initial mid beam mode to the initial high beam mode. Thus, instep S920, if F_(N) equals 1, then the system returns to step S610.Otherwise, the logic and control circuit 34 processes the Sub-Array S(X)in step S930 to determine whether there are any other vehicles (OV) inS(X) in the forward field of view, as previously described. In stepS940, if OV is in S(X), then MC and HC are reset in step S941 and thesystem returns to step S610. If not, then the system goes to step S950.If MC does not equal or exceed MC1, then MC is incremented in step S951and processing returns to step S610. Otherwise, F_(MID) is set andF_(LOW) is reset in step S960, and the logic and control circuit 34outputs control signals to enable the mid beam mode and disable the lowbeam mode in step S970. Next, in step S980, the logic and controlcircuit 34 processes PA(N,M) to determine if there are any othervehicles (OV) in PA(N,M). In step S990, if OV is not in PA(N,M), then HCis incremented and the system returns to step S610. Otherwise, F_(HIGH)is set and F_(MID) is reset in step S1000, after which the logic andcontrol circuit 34 outputs control signals to enable the high beam modeand disable the mid beam mode in step S1010, and the system returns tostep S610.

As discussed, FIG. 13C shows the logic for making transitions from themid beam mode to either low or high beam modes. Thus, if F_(MID) equals1 in step S700 of FIG. 13A, then the logic and control circuit 34processes S(X) for OV in step S710. If OV is in S(X) in step S720,F_(LOW) is set and F_(MID) and MC are reset in step S721, after whichthe logic and control circuit 34 outputs control signals to enable thelow beam mode and disable the mid beam mode in step S722 and the systemreturns to step S610. If OV is not in S(X) in step S720, then the logicand control circuit 34 processes PA(N,M) for OV in step S730. In stepS740, if OV is in PN(N,M), then HC is reset in step S741 and the systemreturns to step S610. Otherwise, in step S750, if HC does not equal orexceed HC1, then HC is incremented in step S751 and processing returnsto step S610. If HC equals or exceeds HCl in step S750, then F_(HIGH) isset and F_(MID) is reset, after which the logic and control circuit 34outputs control signals to enable the high beam mode and disable the midbeam mode in step S770 and then returns to step S610.

Finally, FIG. 13D shows transitions from the high beam mode to the midbeam and low beam modes. Thus, if F_(HIGH) equals 1 in step S800 of FIG.13A, then the system goes to step S810, in which the logic and controlcircuit 34 processes PA(N,M) for OV. In step S820, if OV is not inPA(N,M), the system returns to step S610. Otherwise, F_(MID) is set andF_(HIGH) and HC are reset in step S830, after which the logic andcontrol circuit 34 outputs control signals to enable the mid beam modeand disable the high beam mode in step S840. Next, in step S850, thelogic and control circuit processes S(X) for OV. In step S860, if OV isnot in S(X), then the system returns to step S610. Otherwise, F_(LOW) isset and F_(MID) and MC are reset in step S870, after which the logic andcontrol circuit 34 outputs control signals to enable the low beam modeand disable the high beam mode in step S880 and then returns to stepS610.

Additionally, the above system may also be used to determine anappropriate vehicle lighting configuration and then controlling thevehicle lighting systems so as to improve the driver's forward field ofview. For example, by providing the photosensor array 32 with a forwardfield of view, the system may be used to recognize veiling glare causedby scattered light that may be caused by fog, snow, rain or otheradverse conditions. In particular, the logic and control circuit 34 maybe used to determine a contrast factor representing the level ofcontrast within the forward field of view. This information may then beused to select the appropriate vehicle lighting configuration so as toreduce the level of veiling glare.

The system may also be used to monitor varying windshield surfaceconditions caused by condensation, dirt, rain or snow. In particular,the system may be used to identify these conditions by analyzing theforward field of view image frames for distortion, or degradation. Thiscapability may be enhanced by using infra-red supplemental sourceillumination (SSI) having wavelengths within the responsive range of thephotosensor array 32.

More particularly, since the photosensor array 32 may have a forwardfield of view that includes at least the windshield area, which is sweptby the windshield wipers, the logic and control circuit 34 may be usedto generate control signals to operate the vehicle's windshield wipersystem, windshield washer system, defogger system or windshield de-icingsystem so as to improve forward viewing conditions.

Also, for a forward field of view, the photosensor array 32 may be usedto generate image frame data that controls or supplements the control ofvehicle collision avoidance systems or other automatic vehicle systemsusing forward field of view information. Additionally, since thephotosensor array 32 responds to a portion of the non-visibleelectromagnetic spectrum, as previously described, it may be used toreceive non-visible, spatially or time varying data from objects in theforward field of view, such as vehicles or road signs having aninfra-red source emitter, and to provide vehicle-to-vehicle orroad-to-vehicle communications, which may be used to support intelligentvehicle and highway systems (IVHS), which are designed to improve roadtravel safety and efficiency.

VII. The Automatic Rearview Mirror And Vehicle Interior MonitoringSystem

FIG. 10 also shows the automatic rearview mirror system 20 of thepresent invention. The system 20 is powered by the vehicle's electricalsystem (not shown) to which the system 20 is connected. A voltageregulation and transient protection circuit 22 regulates power andprotects the system 20 from voltage transients as is well known in theart. The circuit 22 is connected to the vehicle's electrical system andto ground, and outputs a voltage of up to about 5 volts to power themirror drive circuits 24 and the light sensing and logic circuit 26. Thecircuit 22 also has a ground line connected to the light sensing andlogic circuit 26.

The 5 volt line is also connected to the force-to-day switch 36 and thereverse-inhibit switch 38 (connected in parallel to the light sensingand logic circuit 26) which are used to force the mirrors 28 to theirmaximum reflectance level. More particularly, when either of theseswitches is closed, they generate a high level signal V_(H) such as a 3volt signal, which is input to the light sensing and logic circuit 26.This high level signal overrides the normal operation of the lightsensing and logic circuit 26 causing it to output a control signal tothe drive circuits 24 to drive the mirrors 28 to their maximumreflectance level. Conversely, when these switches are open, they eachgenerate a low level signal V_(L) such as a signal of less than 3 volts,thereby permitting normal operation of the light sensing and logiccircuit 26, as has been discussed with respect to FIGS. 7, 8A and 8B.The force-to-day switch 36 and the reverse-inhibit switch 38 may bealternatively configured to generate a low level signal when closed anda high level signal when open. The force-to-day switch 36 is a manuallyoperated switch and is preferably placed on the rearview mirror 28a andmay be switch 3. The reverse-inhibit switch 38 is connected to a reverseinhibit line in the vehicle's electrical system (not shown) so that thereverse-inhibit switch 38 is actuated automatically whenever the vehicleis in reverse gear.

The force-to-night switch 40, used to force the mirrors 28 to theirminimum reflectance level, generates a high level signal V_(H) whenclosed and a low level signal V_(L) when opened. The signal V_(H) orV_(L) is then input to the light sensing and logic circuit 26. The highlevel signal may, for example, be between 3 to 5 volts and the low levelsignal may be below 3 volts. The high level signal overrides the normaloperation of the light sensing and logic circuit 26, as discussed withrespect to FIGS. 7, 8A and 8B, causing the circuit 26 to output acontrol signal to the drive circuits 24 to drive the mirrors 28 to theirminimum reflectance level. The low level signal, on the other hand,permits normal operation of the light sensing and logic circuit 26.Alternatively, the force-to-night switch 40 may be configured togenerate a low level signal when closed and a high level signal whenopen. The force-to-night switch 40 is also a manually operable switch,preferably located on the rearview mirror 28a, and may also be switch 3.

The light sensing and logic circuit 26 is also connected to thesensitivity control circuit 42. The circuit 42 enables the operator tomanually adjust the sensitivity of the mirrors 28 using the switch 3(shown in FIGS. 1A and 1B). The sensitivity control circuit 42 (switch3) may comprise a potentiometer whose voltage may be varied from zero tofive volts. Alternatively, a single resistor may be used to provide asingle preset sensitivity setting that cannot be changed by the driver.

As previously discussed with respect to FIGS. 5 and 6, the light sensingand logic circuit 26 comprises the photosensor array 32 (or other lightsensing device) and the logic and control circuit 34. These two devicesmay be either separate or commonly located on a single semiconductorsubstrate. The light sensing and logic circuit 26 is preferably a singleVLSI CMOS circuit.

Also shown in FIG. 10, the light sensing and logic circuit 26 outputsanalog mirror control signals having voltages varying from zero toapproximately 5 volts to the mirror drive circuits 24 and a vehiclelighting control signal of 0 to 5 volts to the vehicle lighting switch45. Alternatively, as previously discussed the light sensing and logiccircuit 26 may output a 5 volt pulse-width-modulated (PWM) signal to themirror drive circuits 24. The mirror drive circuits 24 then generate andapply drive voltages varying from a low voltage on the order of 0 voltsto a high voltage on the order of 1 volt to drive the mirrors 28. Theactual driving voltage (or current) may, of course, be significantlylower or higher depending on the variable reflectance mirror element 1aused.

Each of the mirrors 28 preferably comprises a reflective electrochromic(EC) cell whose reflectance level may be varied from a maximum ofanywhere from approximately 50 to 90 percent to a minimum ofapproximately 4 to 15 percent, and having a maximum driving voltage onthe order of about 1 to 2 volts. As is well known in the art,electrochromic devices change their reflectance level when a voltage orother appropriate drive signal is applied to the electrochromic device.The mirrors 28 alternatively may comprise any other suitable variablereflectance mirror.

As previously discussed, it is also within the scope of the presentinvention for the light sensing and logic circuit 26 to be locatedremotely from the mirrors 28 of the system 20. However, depending onvehicle design and styling requirements, it may be preferred that thelight sensing and logic circuit 26 be integral with the rearview mirror28a such that: (1) the center line of the field of view of thephotosensor array 32 is substantially perpendicular to the reflectivesurface of the rearview mirror 28a; and (2) the horizontal field of viewof the photosensor array 32 is aligned with the horizontal axis of therearview mirror 28a. As a result, the photosensor array 32 receives thelight that will be incident on the rearview mirror 28a as shown in FIG.6.

As has been discussed, the automatic rearview mirror system containingthe photosensor array 32 may be extended to include a vehicle interiormonitoring system configured as a vehicle intrusion detection system byvertically extending the effective field of view of the photosensorarray 32 and by providing vehicle intrusion detection logic in the logiccircuit 26. Importantly, the automotive rearview mirror and vehicleinterior monitoring systems do not have to function simultaneously inboth the vehicle intrusion detection mode and automatic rearview mirrormode. Therefore, the operation of the vehicle intrusion detection modemay be described independently of the operation of the automaticrearview mirror mode. As is described further below, a switch is used toinput a mode select signal to the logic circuit 46 to select the desiredoperating mode.

In the vehicle intrusion detection mode, those photosensor elements 32acorresponding to the image segment below the lower edge of the vehiclewindow areas (i.e., the image information of FIG. 2A excluding the imageinformation FIGS. 3A and 3B) are considered significant. Eachphotosensor element 32a is associated with a small and unique portion ofthe imaged scene. In particular, each photosensor element 32a senseslight within its own image cone. For the preferred photosensor array 32,each photosensor element 32a is responsive to an area approximately one(1) inch square at 100 inches, which is about the maximum distance fromthe photosensor array 32 mounted in the rearview mirror 1 to mostvehicle cabin interior surfaces within the area of interest. For thephotosensor array 32 described above, one set of about 6,400 (160×40sub-array) photosensor elements 32a are used in the automatic rearviewmirror mode and another set of about 12,800 (160×80 sub-array)photosensor elements 32a are used in the vehicle intrusion detectionmode. The ability of the photosensor array 32a to resolve the area ofinterest into a number of data values and to select particular imageinformation, while ignoring other image information, is significant anddistinguishes this vehicle intrusion detection system from other vehicleintrusion detection systems and technologies.

The automatic rearview mirror and vehicle interior monitoring system asshown in the schematic block diagram of FIG. 10A is identical to theautomatic rearview mirror system shown in the schematic block diagram ofFIG. 10 except as follows. First, as explained above, the array sizerequired for an independent automatic rearview mirror system must beexpanded from 160×40 to 160×120 to provide a larger effective field ofview that includes most of the vehicle interior 100. Second, additionallogic or control circuitry is incorporated in logic circuit 46 toprocess the vehicle intrusion detection logic of FIGS. 12 and 12A. Thelight sensing and logic circuit 26 includes additional control inputlines for the "arming" and "alerting" control input signals and controloutput lines to interface with vehicle hardware or vehicle controllersystems. Finally, the regulation and transient protection circuit 22also has an additional vehicle power supply line (12 V BATTERY), and aswitch or other logic for providing a mode select signal that is inputto the light sensing and logic circuit 26.

Normally, power is provided to vehicle hardware through the ignitionswitch controlled power supply circuits to avoid battery drain. Sincethe automatic rearview mirror system operates when the vehicle is beingdriven, it is normally connected to an ignition switch controlled powersupply circuit as shown in FIG. 10. Since the vehicle intrusiondetection system operates when the ignition switch is off, theregulation and transient protection 22 includes the additional vehiclebattery power supply line for supplying power directly from the vehiclebattery. The regulation and transient protection circuit 22 alsoincludes a switch or other logic circuit (not shown) to output a modeselect signal to the light sensing and logic circuit 26. The mode selectsignal is low (0 volts) when power is not available through the ignitionswitch controlled power supply circuit and high (5 volts) when it is.

The light sensing and logic circuit 26 includes an input line to receivean "arming" input signal 49a to actively arm the vehicle intrusiondetection system.

Although not shown in FIG. 10A, other vehicle systems are typically usedto supply an "arming" input signal. Such systems may be actuated byusing conventional infrared or RF type remote control or by theactivation of central door locking systems using the door key or entrycombination keypad.

The light sensing and logic circuit 26 also includes input lines toreceive an "alert" input signal(s) 49b to increase the sampling rate,such as when a trunk lid opening has been detected and increasedmonitoring may be required. The light sensing and logic circuit 26 alsoincludes one or more output signal lines to the vehicle hardware 45aand/or to the vehicle controller system 48, for activating the horn andlights or disabling the ignition control device. The control outputsignal is normally low (0 volts) and goes high (5 volts) when there isan intrusion condition, but may also be a data word providing moredetailed information, (such as the location of the intrusion) to thevehicle controller system.

When power is supplied to the automatic rearview mirror system throughthe ignition switch controlled power supply circuit, the regulation andtransient protection circuit 22 outputs a high (5 volts) mode selectsignal to the logic circuit 46. This causes it to select the automaticrearview mirror mode and the system functions as an automatic rearviewmirror system as previously described.

When the ignition switch is turned off, the mode select signal goes low(0 volts) and the logic circuit 46 sets the system to a low power mode,in which the logic circuit 46 only monitors the status of the modeselect and "arming" control input signals. In this state, the vehicleintrusion detection mode is available, but the system is not "armed" andit is not monitoring the vehicle cabin. When in this state and when the"arming" control input signal is active, then the logic circuit 46enters the vehicle intrusion detection mode described with respect toFIGS. 12 and 12A.

As previously described, in step S301, the logic circuit 46 initializesthe system (e.g., resets the counters, etc., used in the automaticrearview mirror mode) and sets EP to its maximum value and SSI to itsminimum level. Since the lighting levels are not known and may be at anylevel within the full operating range of the system at the time ofarming, the system must determine the optimum combination of EP and SSIby maximizing the number of photosensor elements 32a providing usefulimage data. To minimize system power consumption, the method is biasedto minimize SSI and maximize EP. In step S310, the status of the modeselect, "arming" and "alerting" signals is monitored to confirm theappropriate operating mode. For example, if the "arming" signal goesinactive, then the system returns to a disarmed, low power mode and onlymonitors the mode select and "arming" signals. If there is no statuschange, then the system generates and stores RA.sub.(t) (using stepsS101 to S140 of FIG. 7). The logic circuit 46 ignores RAM array datacorresponding to the 160×40 array of photosensor elements 32a generallyassociated with the window areas as shown in FIGS. 3A and 3B, andprocesses the RAM array data corresponding to the 160×80 array ofphotosensor elements 32a generally associated with the vehicle cabininterior generally excluding the window areas of FIGS. 3A and 3B. Itshould be understood that a trapezoidal sub-set of RAM array data,corresponding to the same sub-set of photosensor elements 32a, may beselected so as to better correspond to the vehicle cabin interiorexcluding the window areas.

In step S320, the logic circuit 46 determines AR by calculating theaverage value of all the values in the selected sub-set of RAM arraydata. In the system described, AR may be in they range 0 to 255 (8-bitdata resolution), but it is preferably at the operating point OP of 127(mid-point of the range); however, for system stability purposes therange factor R results in an operating point OP range of 127±20. In stepS330 and S360, it is determined whether AR is in the range OP±R. If ARis outside the range, then EP and SSI are incrementally increased ordecreased according to steps S341, S342 or S351, S352. This is repeatedfor every image data frame. The system thus optimizes EP and SSI for theparticular circumstances at system startup, and thereafter continues toadjust EP and SSI to maintain AR within the range OP±R as lightingconditions change. If AR is within the range, then the program entersthe primary task S400 in block S370.

The vehicle intrusion detection system is designed to be responsive orsensitive to movement or motion within the vehicle interior 100 andinsensitive to changes in general lighting conditions, moving shadows,etc. The system does this by reducing every image data frame to itsrobust and unique characteristics, largely unaffected by random lightsources or changes in general lighting conditions. After sufficientimage data frames have been processed to allow electrical stabilizationand optimization of EP and SSI, the contour enhanced image data frameRC.sub.(t) is stored as the reference image data frame. Every image dataframe is processed in the same way as the reference image and is thencompared to the reference image. Decisions are reached after severalimages have been compared producing the same result. Three conclusionsare possible after comparing images in the manner described. Images maybe essentially the same, significantly different or neither similarenough nor different enough to make a decision. If this first conditionexists for long enough, changes to the reference image are considered.Confirmation of the differences over several images result in aconcluded intrusion.

More particularly, in step S401, the logic circuit 46 convertsRA.sub.(t) to its contour enhanced form RC.sub.(t) by calculating theaverage difference between the value of RA.sub.(t) for each elementE(n,m) and each of its eight (8) neighbors. As discussed, at systemstart-up, the system must electrically stabilize and must also adjust EPand SSI to optimize the image data frame stored as RC_(REF)(t). This isdone by cycling at least several times from step S310 through steps S403and S404 and then returning to step S310. In step S404, the image dataframe RC.sub.(t) is stored in RAM 50 as RC_(REF)(t) so that RC.sub.(t)and RC_(REF)(t-1) are available in step S402 in RAM 50 for comparison.In step S402, the correlation factor IC for RC.sub.(t) and RC_(REF)(t-1)is determined. During this start-up period, EP and SSI become stable.

In step S403, the start-up criteria are tested, as previously described,and if the count is greater than 25 and the images RC.sub.(t) andRC_(REF)(t-1) correlate (IC exceeds 0.95), then the system continuesthrough step S405. Otherwise, it continues through step S404 until theimage is stable. In the normal monitoring mode, IC is tested against T₁in step S405, where T₁ is 0.6 (T₁ may be less than 0.6). If the degreeof correlation or correspondence between the current and reference imagedata frames is poor (IC is less than 0.6), then the image data framesare judged to be sufficiently different to suggest that vehicleintrusion has occurred. Vehicle intrusion detection systems areevaluated on their ability to detect intrusion conditions and to avoidfalse intrusion conditions. To avoid false intrusion conditions, in stepS408, the number of successive mismatch conditions is counted andcompared to a preset value of 20 (which may be in the range 2 to 300),and a valid intrusion detection condition is established in step S408after 20 successive mismatch conditions. In step S409, the logic circuit46 outputs control signals to vehicle hardware 45a or to the vehiclecontroller system 48 for further processing, which may result in analarm sounding, vehicle immobilization or other appropriate action. Thesystem continues to monitor the vehicle interior or compartment byreturning to step S310. If the number of successive mismatch conditionsfalls below 20 in step S408, then the system returns to step S310.

In step S405, if IC is greater than 0.6, then the images are notsufficiently different to confirm an intrusion condition. It isdesirable to update the reference image data frame RC_(REF)(t) ifchanges occur due to minor and slowly changing conditions outside thevehicle, such as changing light levels or slowly moving shadows due tothe sun tracking across the sky. Accordingly, in step S406, IC iscompared to T₂ (where T₂ is 0.95 but may be in the range 0.95 to 1), andif IC exceeds T₂, then the logic circuit 46 updates and stores thereference image data frame RC_(REF)(t) in step S407. The logic circuit46 may replace RC_(REF)(t-1) with RC.sub.(t) or modify RC_(REF)(t-1) aspreviously described. The system continues to monitor the vehicleinterior by returning to step S310 until the "arming" control inputsignal goes inactive.

It should be understood that the larger field of view provided by the160×120 array of the vehicle intrusion detection system enables furtheranalysis of the rearward scene. Specifically, the background lightsignal B_(t) may be determined using a larger set of photosensor arrayelements 32a. The combination of the automatic rearview mirror detectionsystem and vehicle intrusion detection system additionally provides anopportunity for using SSI to illuminate the vehicle interior under darkconditions for the purpose of precise identification of specific vehiclefeatures such as those indicated in FIG. 2A.

Vehicle feature identification is useful in the automatic rearviewmirror system because it allows the logic circuit 46 to select each ofthe sub-arrays S(X) of photosensor elements 32a corresponding to zonesa, b and c indicated in FIGS. 3A and 3B. This is useful when thephotosensor array 32 is positioned in the rearview mirror 1. Activeadjustment allows the logic circuit 46 to select sets or sub-arrays S(X)of photosensor elements 32a such that zones a, b and c are indicative ofidentical vehicle regions independently of driver rearview mirror 1adjustment.

Finally, to minimize battery power drain, the system described may beoperated in a low power mode by reducing the sampling rate at whichimages are obtained and processed, such as one image data frame persecond. However, if the logic circuit 46 receives an "alerting" controlinput signal such as may be received from a vibration, motion, trunk lidor door opening sensor, then the system described herein may return toits normal sampling rate. Alternatively, this may also be achieved byhaving the system use the lower sampling rate until the logic circuit 46establishes a poor image correlation (i.e., IC<0.6) in step S406 andselects the higher sampling rate.

The vehicle interior monitoring system may also be configured as acompartment image data storage system to store any compartment image,such as the driver image, in the nonvolatile memory 57. The automaticrearview mirror and vehicle interior monitoring system configured as acompartment image data storage system is shown in the schematic blockdiagram of FIG. 10A and the previous description of FIGS. 10 and 10Aapplies except as follows. First, in the specific embodiment describedherein, the light sensing and logic circuit 26 does not use controlinput lines for receiving the "arming" control input signal 49a and the"alerting" control input signal(s) 49b as in the vehicle intrusiondetection system. Second, the additional vehicle power supply line (12 VBATTERY) and mode select signal line are also not used in the specificembodiment described herein. This is because the compartment image datastorage system may be limited to operating when the vehicle has beenstarted since both authorized and unauthorized drivers actuate theignition switch to start the vehicle (the vehicle thief may, of course,break the steering column ignition lock system to do this). Thus, poweris always supplied through the ignition switch controlled power supply(12 V IGNITION) when the vehicle is started. Finally, the light sensingand logic circuit 26 includes input/output lines to interface with thenonvolatile memory/data access logic and port 65, which comprises thenonvolatile memory 57, access/security decoding logic 58 circuit anddata access part 59 of FIG. 6A. To reduce data storage requirements, theimage data frame may be compressed using any appropriate digital imagecompression technique as discussed with respect to FIG. 6A. The imagedata frame is then stored in the nonvolatile memory 57, such as anEEPROM or any other appropriate nonvolatile memory, which has sufficientstorage to store a predetermined number of image data frames.

The compartment image data storage system may be configured to store asingle image data frame in the nonvolatile memory 57 for each ignitioncycle. When power is supplied to the automatic rearview mirror systemthrough the ignition switch controlled power circuit, the regulation andtransient protection circuit 22 supplies 5 volts to the light sensingand logic circuit 26, which begins system initialization for a setperiod of between zero (0) seconds and two (2) minutes, but preferably30 seconds. This delay condition or wait state reduces the opportunityfor vehicle thieves to detect SSI which may be emitted during the imageoptimization process of FIG. 12. After the wait state has ended, thecompartment image data storage system operates as has already beendescribed with respect to FIGS. 12A and 12B. The nonvolatile memory 57should be sufficiently large to store a number N of valid image dataframes RA.sub.(t) to document N sequential ignition cycles where N is inthe range of 2 to 10, but is preferably 5. The image data frames areaddressed via pointers that select a general memory location which areused to store each valid image data frame RA.sub.(t). The pointeraddressing scheme is cycled on a first-in-first-out (FIFO) basis so thatthe most recent valid image data frames replace the "oldest" image dataframes in the nonvolatile memory 57. After storing a valid image dataframe RA.sub.(t), the system ends cycling and enters a dormant statewaiting for the next ignition cycle.

Alternatively, multiple valid image data frames may be stored for asingle ignition cycle. This second version of the compartment image datastorage system performs exactly as the first description except asfollows. After storage of the initial image data frame, the systemreturns to step S310 and the logic circuit 46 generates a random waitstate ranging from 8 to 15 minutes during which the system stopsgenerating image data frames. After the wait state has ended, the systemproceeds to attempt generate another valid image data frame. This cycleof randomly waiting and then attempting to generate valid image dataframes is continued as long as the ignition supplies power to thesystem. This approach is more difficult for thieves to defeat. Thissystem may also be configured as a realtime image data storage system(e.g., 30 frames per second). Of course, since at least several hundredimage data frames may need to be processed, compressed and stored in thenonvolatile memory 57, the processing and nonvolatile memory storagerequirements are significantly greater than for the other image datastorage systems described above. An initiation sensor, such asaccelerometers, motion sensors, vibration sensors or any other sensorcapable of detecting vehicle motion, inputs an initiation signal, andafter receiving the initiation signal, the light sensing and logiccircuit 26 generates and stores in real-time the image data frames for apredetermined period, such as 10 seconds.

The nonvolatile memory 57 is preferably housed in a separate module in aphysically difficult to access location within the vehicle, such as highon the fire wall behind the instrument cluster. The module is preferablya durable metal housing or other housing sufficiently durable so that itwill protect the nonvolatile memory 57 from extreme shock or heat, suchas might occur in a vehicle accident. To better ensure that the imagedata frames in the nonvolatile memory 57 are not accessed byunauthorized personnel, access may be limited by the securityaccess/decoding logic 58. The security access codes necessary to accessthe image data frames may, for example, be distributed only toauthorized persons. When the proper security access code is entered, theimage data frames may be accessed through the access port 59; typically,the access port 59 is a multi-pin connector to which a data retrievalsystem may be connected.

It should be understood that the vehicle interior monitoring systemdescribed above, including the vehicle intrusion detection system andthe compartment image data storage system configurations, may beimplemented as an independent or stand-alone system in a module (withoutthe automatic rearview mirror system), and that it may be mountedindependently within the vehicle, such as in the headliner, headlinerconsole or other appropriate areas.

The performance of the vehicle interior monitoring systems describedherein may be enhanced by providing enhanced infrared reflectancecharacteristics in certain areas within the vehicle interior 100. Forexample, some fibers (such as cotton and silk) tend to reflect nearinfrared illumination better than other fibers (such as nylon and rayon)which tend to absorb near infrared illumination. Therefore, a patternmay be established in the vehicle interior 100 such as on the driverseat 101 or passenger seat 102 or front or rear seats or on thevehicle's interior door panels, etc., by using different fibers or othermaterials to establish a pattern, such as a grid or any otherappropriate pattern. Near infrared illumination of the pattern providesa higher contrast image to the photosensor array 32. This better ensuresthat the logic circuit 46 accurately determines, for example, thepresence of an intruder, an occupant or other object (such as a childrestraint system in the front passenger seat).

Using fibers or materials having better infrared reflectancecharacteristics as described above is useful both during the day and atnight. During the day, any near infrared reflective pattern in thevehicle will generally provide a higher contrast pattern to thephotosensor array 32 because of natural sources (sunlight) orsupplemental sources of near infrared of illumination. In particular, iflight levels fall below some predetermined level (typically in the rangeof about 0.1 lux to 5 lux), then near infrared SSI may be used toprovide a higher contrast image pattern to the photosensor array 32.

The vehicle interior monitoring system may also be used to monitor thevehicle interior 100 to determine whether there is an adult occupant, achild restraint system or no occupant in the front or rear passengerseat areas. Various mechanical and electrical sensors have beenconsidered or used for detecting or sensing the size and presence ofvehicle occupants, particularly those in the front passenger seat. Thesesensors include pressure sensors (mechanical and solid-state),accelerometers, ultrasonic sensors and mechanical or electrical switchmechanisms for indicating seat belt use. As air bags are becoming moreprevalent, vehicle owners, insurance companies and automotive companieshave a strong interest in having air bags deploy properly at all times,since replacing deployed airbags is costly. Additionally, there has beensome discussion as to whether air bags should deploy when there is achild restraint system that is positioned rearwardly facing in the frontpassenger seat. Since performance requirements are stringent for safetyrelated components, it is problematic to make appropriate airbagdeployment decisions using currently known sensor technologies. Thevehicle interior monitoring system may be configured as a vehicleoccupant detection system that may be used to aid in the intelligentdeployment of air bags depending, for example, on the status of thevehicle occupant. Image information, such as size, shape, contour andmotion may be processed by the logic circuit 46 to determine whether tooutput a control signal to the air bag deployment system to prevent anair bag from deploying (such as a passenger air bag when there is nofront seat passenger) or for controlling the rate at which the airbagdeploys.

The individual components represented by the blocks shown in theschematic block diagrams of FIGS. 6, 6A, 6B, 10 and 10A are well knownin the art relating to automatic rearview mirrors, vehicle lightingsystems and vehicle intrusion detection systems, and their specificconstruction and operation is not critical to the invention or the bestmode for carrying out the present invention. Moreover, the logic flowcharts discussed in the specification and shown in FIGS. 7, 8A, 8B, 12,12A, 12B, 13A, 13B, 13C and 13D may be implemented in digital hardwiredlogic or programmed into well-known signal processors, such asmicroprocessors, by persons having ordinary skill in the art. Since suchdigital circuit construction or programming per se is not part of theinvention, no further description thereof is deemed necessary.

While the present invention has been described in connection with whatare the most practical and preferred embodiments as currentlycontemplated, it should be understood that the present invention is notlimited to the disclosed embodiments. Accordingly, the present inventionis intended to cover various modifications and equivalent arrangements,methods and structures that are within the spirit and scope of theclaims.

What is claimed is:
 1. A system for monitoring a vehicle interior, comprising:photosensor array means, disposed in a vehicle interior in a top portion of the vehicle, for sensing light levels in an area rearward of said photosensor array means and generating at least a first set of photosensor array signals; first determining means coupled to said photosensor array means for receiving said at least a first set of photosensor array signals, and for determining a first signal from a first number of said at least a first set of photosensor array signals; second determining means coupled to said photosensor array means for receiving said at least a first set of photosensor array signals, and for determining a second signal from a second number of said at least a first set of photosensor array signals, the second number being greater than the first number, the second signal including signals corresponding to image information from the vehicle interior; and memory means coupled to said second determining means for receiving and storing said second signal.
 2. A system according to claim 1, wherein said second determining means determines the second signal by receiving the second number of array signals from a portion of said photosensor array means below the portion of said photosensor array means which provides the first number of array signals.
 3. A system according to claim 1, further comprising switch means for switching said system between a first mode wherein the first determining means determines the first signal, and a second mode wherein the second determining means determines the second signal.
 4. A system according to claim 1, further comprising arming means for activating said second determining means.
 5. A system according to claim 1, further comprising a vehicle battery power supply line for supplying power directly to said system from a vehicle battery.
 6. A system according to claim 1, further comprising alerting means for increasing a sampling rate of said photosensor array means in response to a predetermined condition.
 7. A vehicle intrusion detection system for detecting movement within a vehicle interior of an automotive vehicle, comprising:photosensor array means, disposed in a top portion of the vehicle, for sensing light levels in an area including at least a portion of a vehicle interior, and for generating at least a first set and a second set of photosensor array signals; determining means coupled to said photosensor array means for receiving said at least a first set and a second set of photosensor array signals, and for determining at least a first set and a second set of values indicative of said at least a first set and a second set of photosensor array signals; and comparing means coupled to said determining means for receiving said at least a first set and a second set of values indicative of said at least a first set and a second set of photosensor array signals, and for comparing said at least a first set and a second set of values to generate an alarm signal when the comparison between said at least a first set and a second set of values corresponds to a predetermined intrusion condition.
 8. A system according to claim 7, further comprising a vehicle power supply line for providing power from a vehicle battery to said system.
 9. A system according to claim 7, wherein said photosensor array means, said determining means, and said comparing means are disposed in a vehicle rearview mirror housing.
 10. A system according to claim 7, further comprising means responsive to said alarm signal to activate a vehicle horn and/or vehicle lights.
 11. A system according to claim 7, further comprising means responsive to said alarm signal for disabling a vehicle ignition control device.
 12. A system according to claim 7, further comprising arming means for activating said comparing means.
 13. A compartment image data storage system for an automotive vehicle, comprising:photosensor array means, disposed in a top portion of the vehicle, for sensing light levels in at least a portion of a vehicle compartment and generating at least a first set of photosensor array signals; processing means coupled to said photosensor array means for receiving said at least a first set of photosensor array signals and determining at least a first set of values corresponding to said at least a first set of photosensor array signals, said first set of values excluding values corresponding to a window portion of the vehicle compartment; and memory means coupled to said processing means for receiving and storing said at least a first set of values indicative of said at least a first set of photosensor array signals.
 14. A system according to claim 13, wherein said memory means stores a plurality of images.
 15. A system according to claim 13, wherein said processing means determines a plurality of sets of values corresponding to a plurality of sets of photosensor array signals corresponding to a plurality of images taken at a predetermined timing.
 16. An automatic rearview mirror system for an automotive vehicle comprising:a variable reflectance rearview mirror having a casing; a photosensor array means for sensing light levels in an area rearward of said variable reflectance rearview mirror and for generating photosensor array signals; a signal processing means for receiving said photosensor array signals and for determining from said photosensor array signals a signal for controlling said variable reflectance rearview mirror; and a mounting bracket means for attaching said variable reflectance rearview mirror casing to said automotive vehicle, said mounting bracket means further comprising a housing means for housing said photosensor array means and said signal processing means.
 17. A system according to claim 16, wherein said mounting bracket means houses said photosensor array means at a position below said mirror casing.
 18. A system according to claim 16, further comprising a mirror function switch disposed in said mounting bracket means. 